WOOD 

:    AND -ITS- USES    '. 

C-F-CF          J-BEVAN 
::    R-V  VLL    :: 


LIBRARY 

OF  THB 

UNIVERSITY  OF  CALIFORNIA. 

Class 


s  >:    * 


Westminster"  Series 


WOOD    PULP    AND    ITS    USES 


WOOD  PULP 

AND  ITS  USES 

BY 
C.    F.    CROSS,    E.   J.    BEVAN 


AND 


R.    W.    SINDALL 

WITH   THE   COLLABORATION   OF 

W.     N.     BACON 


NEW    YORK 

D.   VAN    NOSTRAND   COMPANY 

23    MURRAY   AND   27    WARREN    STREETS 
1911 


A 


PREFACE 

THE  world  has  had  its  Stone  age  and  its  Bronze  age  :  later 
its  Iron  age,  and  the  present  is  a  Cellulose  age. 

This  is  not  said  ad  captandum ;  it  is  a  statement  which 
will  survive  critical  examination. 

The  volume  now  offered  to  students  and  the  general  public 
is  based  on  studies  in  the  domain  of  cellulose,  both  theo- 
retical and  scientific,  and  practical  or  industrial. 

It  is  not  a  monograph  or  a  text-book  of  the  subject :  it 
does  not  pretend  to  be  systematic  or  exhaustive. 

Technical  literature  in  these  days  threatens  to  develop  to 
formidable  dimensions;  and  systematic  works  on  branches 
of  technology  necessarily  carry  a  large  weight  of  fact  and 
information  which  is  common  groundwork. 

We  have  only  given  an  outline  of  what  appears  essential 
as  a  cyclopaedic  framework.  We  are  not  addressing  our- 
selves particularly  to  the  specialist,  nor  to  the  technical 
student.  Rather  to  the  general  reader,  and  our  aim  is 
therefore  to  give  a  general  account  of  the  evolution 
of  the  wood  pulp  industries,  as  typical  of  the  age  we  live 
in,  and  as  a  very  substantial  contribution  to  its  primary 
necessities. 

But  if  wood  pulp  has  had  an  interesting  past  history,  its 

221874 


vi  PEEFACE 

future  is  suggestive  of  many  more  interesting  possibilities 
of  which  we  endeavour  to  give  indications. 

From  whatever  standpoint  in  fact  the  subject  is  treated, 
it  challenges  attention. 

The  chemist,, the  manufacturer,  the  political  economist, 
and  of  course  the  financier  will  find  that  it  teems  with  pro- 
blems the  solution  of  which  carries  rewards  of  great  moment. 

In  an  age  when  pessimists  see  little  but  competitive 
exhaustion  of  sources  of  natural  wealth,  it  is  satisfactory  to 
be  able  to  present  a  domain  still  full  of  unexplored  possi- 
bilities. Such  is  the  subject  of  "wood  pulp"  or,  more 
broadly,  "cellulose,"  and  we  trust  this  imperfect  contribution 
will  help  to  sustain  and  awaken  the  interest  of  readers  and 
students. 

We  have  pleasure  in  acknowledging  the  valuable  assistance 
of  Mr.  W.  N.  Bacon  B.Sc.,  F.I.C.,  in  contributing  matter 
and  revising  proofs. 

We  are  indebted  to  the  Royal  Society  for  the  privilege 
of  reproducing  illustrations  from  papers  of  the  late  W.  J. 
Eussell  (p.  73).  To  Messrs.  Longmans,  for  permission  to 
reproduce  portions  of  "  Researches  on  Cellulose,"  II. 

The  illustrations  in  Chapter  I.  are  chiefly  from  original 
histological  studies  of  Messrs.  Flatters,  Milborne  and 
McKeoiiine  (Longsight,  Manchester),  whose  excellent  work 
in  this  field  is  well  known,  or  should  be,  to  all  students  of 
Botany. 


CONTENTS 


CHAP.  PAGE 

I.      THE   STRUCTURAL   ELEMENTS   OF   WOOD      .  .  .  1 

II.  I.  CELLULOSE  AS  A  CHEMICAL  INDIVIDUAL  AND 
TYPICAL  COLLOID.  II.  THE  LIGNONE  COM- 
PLEX, LIGNO-CELLULOSE  ;  SPECIAL  CHEMICAL 
NOTE  ON  AUTOXIDATION,  AND  RESEARCHES  OF 
W.  J.  RUSSELL  ...  .  .  .  .  29 

* 

III.  WOOD   PULPS   IN   RELATION  TO   SOURCES   OF   SUPPLY  : 

FOREST   TREES   AND    FORESTRY  .  .  .         76 

IV.  THE   MANUFACTURE   OF   MECHANICAL   WOOD    PULP       .         96 
V.      CHEMICAL   WOOD    PULP      .  .  .  .  .  .      120 

VI.  NEWS   AND    PRINTINGS        .            .            .            .  .  .•     178 

VII.  WOOD   PULP  BOARDS            .           .           .           ,  .  .      190 

VIII.  THE   UTILISATION   OF   WOOD    WASTE.           .  '.  .198 

IX.  TESTING   OF   WOOD   PULP   FOR   MOISTURE   .  .  206 

X.  WOOD   PULP   AND   THE   TEXTILE   INDUSTRIES  .  .215 

XI.  SPECIMEN   PAGES — VARIOUS   TYPES    OF   PAPER   .  .251 

BIBLIOGRAPHY  .  263 


INDEX  265 


LIST  OF  ILLUSTRATIONS 

FIG.  PAGE 

1.  TRANSVERSE     SECTION     OF     STEM     OF     TRADESCANTIA 

SHOWING  EPIDERMAL  TISSUE,  PARENCHYMA  CON- 
TAINING STAKCH,  AT  THE  CENTRE  A  VASCULAR 
BUNDLE  . 5 

2.  TRANSVERSE    SECTION    OF    A    YOUNG    STEM    OF   PINUS 

SYLVESTRIS  (COMMON  PINE).  BELOW,  PRIMARY 
GROUND  TISSUE  FOLLOWED  BY  WOOD  IN  DEVELOP- 
MENT AND  IN  SUCCESSION  CAMBIUM  BAST  AND 
CORTEX.  IN  THE  CENTRE  IS  A  MEDULLARY  RAY  6 

2B.  TRANSVERSE  SECTION  OF  AN  OLDER  STEM  OF  PINUS 
SYLVESTRIS  (COMMON  PINE)  SHOWING  DEVELOP- 
ING BRANCH,  A  MORE  ADVANCED  WOOD  SYSTEM 
AND  EXTERNAL  TO  THE  LATTER  THE  CAMBIUM 
AND  PHLOEM  TISSUES 7 

3.  LONGITUDINAL     SECTION     VASCULAR    BUNDLE    OF    ZEA 

MAIS  SHOWING  SPIRAL,  ANNULAR,  AND  PITTED 
VESSELS.  SURROUNDING  THE  BUNDLE  IS  THE 
GROUND  TISSUE  OR  PARENCHYMA  ...  8 

4.  LONGITUDINAL    SECTION   OF   STEM    OF    GOSSYPIUM   S.P. 

(COTTON  PLANT)  SHOWING  FROM  LEFT  TO  RIGHT 
PITH,  SPIRAL  VESSELS,  CAMBIUM,  PHLOEM,  COR- 
TICAL TISSUE,  AND  CUTICLE  .  .  .  .  9 

5.  TRANSVERSE   SECTION  OF   STEM   OF  ZEA  MAIS    (INDIAN 

CORN).  VASCULAR  BUNDLES  SURROUNDED  BY 
PRIMARY  GROUND  TISSUE.  EACH  BUNDLE  CONTAINS 
LARGE  PITTED  AND  ANNULAR  VESSELS  WITH 
PHLOEM  AND  SCLERENCHYMA  10 


x  LIST  OF  ILLUSTEATIONS 

FIG.  PAGE 

5B.  JUTE — SECTION  OF  BAST  REGION  SHOWING  WEDGE- 
SHAPED  BUNDLES  EXTENDING  FROM  CAMBIUM  TO 
CORTEX  ;  .  .  *  ...  11 

5c.  JUTE  (MAG.  300)— SECTION  OF  BAST  REGION  SHOWING 

STRUCTURE  OF  BUNDLES  AND  THICKENING  OF 
ULTIMATE  FIBRES  .  .  .  •  '.."•  .  12 

5D.  FLAX— SECTION  OF  STEM  OF  LINUM  SHOWING  GROUPS 
OF  BAST  FIBRES  LYING  BETWEEN  WOOD  AND 
CORTEX  .  .  .  .  .  .  .13 

G.  TRANSVERSE  SECTION  OF  STEM  OF  LYMNAKTHEMUM 
(AQUATIC  PLANT).  CENTRAL  AXIS  WITH  XYLEM 
AND  PHLOEM  ELEMENTS.  GROUND  TISSUE  SHOW- 
ING LARGE  AIR  CELLS  PRODUCING  BUOYANCY,  AND 
STAR-SHAPED  IDIO BLASTS  .  .  .  .  .  14 
7.  TRANSVERSE  LONGITUDINAL  SECTION  OF  STEM  OF 
TILIA  EUROPCEA  (LIME  TREE),  SHOWING  BAST 
FIBRES  AND  GROUND  TISSUE  .  .  .  .  '  15 

8.  TANGENTIAL  LONGITUDINAL    SECTION   THROUGH   THE 

WOOD  ELEMENTS  OF  TILIA  EUROPCEA  (LIME  TREE). 
FROM  LEFT  TO  RIGHT  A  MEDULLARY  RAY  IS  SEEN 
IN  THE  ROW  OF  LITTLE  CELLS,  FOLLOWED  BY 
TYPICAL  WOOD  FIBRES,  SPIRAL  AND  PITTED  VES- 
SELS, AND  CONNECTIVE  TISSUE  .  .  v  .  16 

9.  LONGITUDINAL  RADIAL  SECTION  OF  PINUS  SYLVESTRIS 

TIMBER    SHOWING    WELL-DEVELOPED    BORDERED 
PITS  UPON  THE  WALLS  OF  THE   TRACIIE1DS.    AT 
RIGHT  ANGLES  TO  THE  TRACHEIDS  IS  A  MEDUL- 
LARY  RAY     .          ..  •  •  •  •  •  •         17 

10.  TANGENTIAL  LONGITUDINAL  SECTION  OF  OLD  WOOD 
OF  PINUS  SHOWING  TRACHEIDS  AND  MEDULLARY 
RAYS  ;  THE  LATTER  CONSIST  OF  TWO  OR  MORE 
ROWS  OF  CELLS  ARRANGED  LONGITUDINALLY  18 


LIST- OF  ILLUSTRATIONS  xi 

Fl«.  PAGE 

11  A.  TRANSVERSE  SECTION  OF  STEM  OF  GOSSYPIUM  (COTTON 
PLANT)  SHOWING  ONE  ANNULAR  RING  OF  XYLEM 

AND    PHLOEM     ELEMENTS    WITH    INTERVENING 
CAMBIUM  LAYER  .        .        .        .        .        .        .      19 

llB.  TRANSVERSE  SECTION  OF  A  THREE-YEAR-OLD  STEM  OF 
TILIA  (LIME  TREE).  AT  CENTRE  PITH  THEN  XYLEM 
(WOOD)  IN  THREE  SEPARATE  RINGS.  TOWARDS 
THE  PERIPHERY  THE  CAMBIUM  RING  THEN  PHLOEM 
AND  CORTICAL  TISSUE  •  .  .  .  .  ,  21 

12.  DATE   PALM.      TYPICAL   MONOCOTYLEDON   PERENNIAL    .         22 

12B.  PINE.      TYPICAL   CONIFER.      EXOGENOUS   GYMNOSPERM.         23 

12C.  OAK.      TYPICAL   ANGIOSPERM   EXOGENOUS   PERENNIAL  .         24 
13A.    LARCH        V          •-         •           •           •           •           •         '•            •         73 

13B.  OAK  .            .          V         .            .            .           .           ..           .           1  -      73 

13C.  SPRUCE                   ......            .            .           .           .         74 

13D.  SCOTCH    Flit          ;           .          ..;•'•'         ..           .           .           .           .        74 

14.  VIEW   OF   HORIZONTAL  GRINDER  (A),  WITH  SECTION  (B)         98 

15.  CURVE   FOR    ILLUSTRATING   POWER   TRIALS  .  .      103 

16.  SHAKING    SCREEN         .  .  .  .  ...  .105 

17A.  CENTRIFUGAL   SCREEN   FOR   WOOD    PULP        .           .            .106 

17B.  SECTION  OF   CENTRIFUGAL   SCREEN   FOR    WOOD   PULP     .      107 

18.  DIGESTOR  FOR  MANUFACTURE  OF  BROWN  PULP  .  .110 

19.  TOWER  BLEACHING  PLANT         .        .        .        .  .    143 

20.  HAAS  AND  OETTEL  ELECTROLYSER     .        i  -      .  .     167 

21.  CHLORINE  CAUSTIC  SODA  CELL  (SECTION)  .        .  .    169 

22.  THE  "HOLLANDER"  BEATING  ENGINE        .        .  .     185 
23  AND  2 3 A.    DIAGRAMS  OF  WEDGE  SYSTEM     .        .  .210 

24.  SPINDLE  FOR  TWISTING  PAPER-STRIPS       ..        .        .    222 

25.  MACHINE  FOR   ROLLING   FLAT  STRIPS  OF   PREPARED 

SHORT    FIBRE    (SLIVER)       ...  .  .  .      224 


WOOD  PULP  AND  ITS  USES 


CHAPTER  I 

THE    STRUCTURAL    ELEMENTS   OP   WOOD 

THERE  are  no  more  interesting  studies  than  those  which 
group  themselves  under  the  term  Applied  Sciences.  It  is 
quite  true  that  science,  or  rather  the  sciences,  may  be 
pursued  from  a  point  of  view  which  ignores  the  services 
which  they  render  to  man ;  but  whereas  "  pure  science  " 
is  an  ideal  rather  of  the  imaginative  world,  the  natural 
prosecution  of  the  sciences  compels  the  recognition  of  their 
organic  interdependence  with  human  progress. 

Whichever  aspect  is  the  more  attractive  on  general 
grounds,  it  is  clear  that  the  subject  of  this  work  is  pro- 
minently typical  of  this  interdependence ;  involves  in  a 
particular  manner  the  utilitarian  bearings  of  science,  and 
our  treatment  of  it  must  be  accordingly  utilitarian. 

Wood  pulp  is  a  comparatively  modern  product  called  into 
existence  as  a  paper  maker's  raw  material.  The  woods 
which  furnish  the  product  in  its  various  forms  have  been 
impressed  into  the  service  of  man  from  the  earliest,  in 
fact  from  prehistoric,  times,  and  have  been  used  for 
their  structural  qualities  in  a  large  number  of  our  most 
important  industries.  The  uses  of  the  woods  are  so 

W.P.  B 


2  WOOD   PULP  AND  ITS  USES 

universally  familiar  that  it  would  be  superfluous  to 
particularise  them. 

We  may,  however,  preface  our  specialisation  to  the  par- 
ticular employment  of  certain  woods  as  the  basis  of  wood 
pulp,  by  calling  attention  to  the  physical  and  mechanical 
properties  of  a  typical  range  of  woods  considered  as 
structural  materials. 

For  the  natural  history  of  the  woods  as  products  of 
vegetable  life  and  growth  we  turn,  of  course,  in  the  first 
instance  to  the  science  of  Botany.  In  the  scientific  treat- 
ment of  plant  life  questions  of  utility — that  is,  the  part 
which  a  plant  or  any  of  its  parts,  seed,  flower,  stem  or  root, 
may  play  in  the  service  of  man — has  no  part.  Moreover, 
external  features  are  of  quite  subordinate  moment. 

Thus  the  cereals  which  furnish,  perhaps,  the  most 
important  staple  of  our  food  are  to  the  botanist  no  more 
important  than  any  other  of  the  great  family  of  the  grasses. 
It  is  not  without  significance  to  the  botanist  that  these 
particular  grasses  have  come  to  be  selected  and  specialised 
by  cultivation  through  countless  generations,  so  as  to 
differentiate  them  as  economic  products.  But  such  con- 
siderations are  relatively  unimportant,  as  not  concerned 
in  those  elements  of  identity  and  characterisation  which  fix 
the  position  of  an  individual  plant  in  the  scheme  of  botanical 
science. 

So  also  in  regard  to  external  features  such  as  size,  form, 
and  vegetative  habit.  The  sugar  cane  or  bamboo  are  not 
obviously  related  to  the  cereals,  but  to  the  botanist  the 
relationship  is  of  the  closest.  The  laburnum  and  the 
trefoil  have  little  in  common  as  regards  form  and  life 
history,  but  they  are  blood  relations. 


THE  STRUCTURAL  ELEMENTS  OF  WOOD  3 

The  relationships  are  fixed  by  the  more  fundamental 
features  of  the  reproductive  mechanism ;  both  the  major 
and  minor  differentiations  constituting  the  basis  of  the 
classifications  of  botanical  science  are  those  of  the  repro- 
ductive system.  These  differences  necessarily  are  corre- 
lated with  those  of  the  plant  body,  by  which  the  second 
great  function  or  group  of  functions  is  conditioned, 
viz.,  those  of  nutrition.  As  the  reproductive  mechanism 
becomes  more  complex,  so  the  structural  type  is  differen- 
tiated towards  complexity.  Viewing  the  plant  world  as  an 
evolutionary  series,  reproduction  by  seeds  is  the  last 
feature  to  make  its  appearance,  and  is  preceded  by  those 
differentiations  of  the  plant  body  which  issues  in  what  is 
known  as  a  vascular  system. 

Thus  in  the  fern  the  structural  features  of  the  higher 
flowering  and  seed-bearing  plants  are  recognised,  and  in  a 
tree  fern  the  differentiation  into  vascular  tissue,  leaves  and 
stems,  with  the  lower  portion  formed  into  a  root  system, 
are  apparent.  But  the  reproduction  of  the  fern  is  on  a 
much  lower  plane,  and  it  bears  no  seeds.  The  tree  fern  is 
a  kind  of  pseudo-morph  of  the  true  tree  or  forest  tree,  which 
is  a  spermatophyte  or  seed-bearing  plant. 

Of  the  four  great  groups  of  modern  botanical  classifica- 
tion the  spermatophytes  are  much  the  most  conspicuous 
and  widely  distributed.  Moreover,  they  are  so  interwoven 
with  our  experience  that  their  study  has  often  ranked  as 
co-extensive  with  botanical  science  to  the  exclusion  of  the 
other  great  groups.  These  are  the  algae,  the  lichens,  and 
the  fungi  (Thallophytes),  the  mosses  (Bryophytes),  and  ferns, 
horsetails,  and  club  mosses  (Pteridophytes).  The  modern 
science  regards  these  groups  as  related  in  evolutionary 

B  2 


4  WOOD  PULP  AND  ITS  USES 

sequence.  There  are  two  aspects  of  this  evolution.  The 
one  involves  the  theory  of  descent,  the  higher  from 
the  lower  order,  as  an  objective  fact;  on  the  other  the 
development  of  the  highest  type  can  be  followed  through 
the  lower  by  the  study  of  the  dominant  or  reproductive 
functions,  which  thus  unfolds  itself  as  a  homogeneous  con- 
ception of  the  relations  of  the  infinitely  diversified  forms  of 
plant  life. 

We  are  not  concerned  with  these  fundamental  generalisa- 
tions further  than  to  indicate  their  connection  with  our 
subject. 

We  shall  have  to  point  out  that  from  the  point  of  view 
of  "wood  pulp"  the  trees  which  furnish  these  industrial 
products  are  of  two  sub-groups,  and  we  have  explained  the 
basis  of  classification  sufficiently  to  convey  their  relationship 
to  the  general  reader  in  the  terms  employed  by  the 
botanist  :— 

Spermatophytes 
(seed-bearing  plants) 

Gymnosperms  Angiosperms 

(naked  or  exposed  seeds)  (enclosed  seeds) 

Monocotyledons     Dicotyledons 
(Coniferae)  Bamboo  Poplar 

Pine     Spruce  Sugar  Cane. 

We  have  already  indicated  that  our  subject  has  only  an 
incidental  connection  with  these  fundamental  relations. 
The  plant  is  a  structure,  an  agglomerate  of  structural 
elements ;  and  its  work  as  a  plant  is  to  grow,  to  build  up 
tissue  The  assimilating  organs  of  the  higher  flowering 


THE  STRUCTURAL  ELEMENTS  OF  WOOD      5 

plants  are  the  leaves.     The  leaf  is  the  centre  of  the  funda- 
mental operation  of   building   up    "  organic "   compounds 


FIG.  1. — Transverse  section  of  stem  of  Tradescantia 
showing  epidermal  tissue,  parenchyma  containing 
starch,  at  the  centre  a  vascular  bundle. 

from  the  inorganic  form  of  carbon,  viz.,  carbonic  anhydride, 
contained  in  the  air,  and  of  which  gaseous  mixture  it  is  a 
normal  constituent.  This  characteristic  function  of  the 


6  WOOD  PULP  AND  ITS  USES 

plant,  the  photosynthesis  of  carbon  compounds  and  their 


FIG.  2. — Transverse  section  of  a  young  stem  of  Pinus 
Sylvestris  (common  pine).  Below,  primary  ground 
tissue  followed  lay  wood  in  development  and  in 
succession  cambium  bast  and  cortex.  In  the  centre 
is  a  medullary  ray. 

elaboration  to  tissue  material,  we  must  take  for  granted ; 
as  well  as  the  complementary  function  of  the  root  system 


THE  STKUCTUEAL  ELEMENTS  OF  WOOD      7 

in  absorbing  water,  inorganic  mineral  compounds,  and  other 
nutrient  material  from  the  soil. 


FIG.  2s. — Transverse  section  of  an  older  stem  of  Pinus 
Sylvestris  (common  pine)  showing  developing 
branch,  a  more  advanced  wood  system  and  external 
to  the  latter  the  cambium  and  phloem  tissues. 

We  are  concerned  with  the  plant  as  a  completed  struc- 
ture.   The  study  of  those  functions  and  processes  from  which 


8  WOOD   PULP  AND  ITS  USES 

the  structure  results,  and  with  which  it  is  in  its  several 
parts   associated,    constitutes   the   branch   of    the   science 


FIG.  3.— Longitudinal  section  vascular  bundle  of  Zea 
Mais  showing  spiral,  annular,  and  pitted  vessels. 
Surrounding  the  bundle  is  the  ground  tissue  or 
parenchyma. 

known  as  vegetable  physiology;  and  students  who  desire 
a  more  comprehensive  survey  of  the  subject-matter  are 
referred  to  the  special  text-books. 


THE  STRUCTURAL  ELEMENTS  OF  WOOD     -9 

Taking  the  plant  as  a  structure,  \ve  find  it  an  assemblage 
of  units  generally  known  as  cells.     The  typical  cell  is  a 


FIG.  4. — Longitudinal  section  of  stem  of  Gossypium  S.P. 
(cotton  plant)  showing  from  left  to  right  pith,  spiral 
vessels,  cambium,  phloem,: cortical  tissue,  and  cuticle. 

spherical   body   of   small   dimensions — O'l    and   0'5   mm, 


10 


WOOD   PULP  AND  ITS  USES 


diameter — and  consisting  of  an  enveloping  wall  enclosing 
the  cell  contents. 


FIG.  5. — Transverse  section  of  :| stem  of  Zea  Mais  (Indian 
corn).  Vascular  bundles  surrounded  by  primary  ground 
tissue.  Each  bundle  contains  large  pitted  and  annular 
vessels  with  phloem  and  sclerenchyma. 

Variations  and  differentiations  of  the  typical  form  corre- 
spond with  infinite  diversity  of  functions  and  conditions. 
Typical  forms  of  cellular  tissue  are  represented  in 
Figs.  1—2. 


THE  STKUCTUBAL  ELEMENTS  OF  WOOD 


11 


More  extreme  variations  lead  to  the  structural  forms 
classed  as  fibres  and  vessels. 

These  are  elongated  cells,  the  length  being  a  very  large 
multiple  of  the  diameter.  In  a  general  way  "  fibres " 
may  be  regarded  as  the  strengthening  elements  of  plant 
structures,  and  are  of  relatively  simple  form.  "  Vessels  "  are 


Jute. 

FIG.  OB.— Section  of  bast  region  showing  wedge-shaped 
bundles  extending  from  cambium  to  cortex. 

the  seat  of  complex  vital  functions  and  operations  involved 
in  nutrition,  and  are  much  more  diversified  in  form. 
Typical  fibres  and  vessels  are  represented  in  Figs.  3 — 4. 

The  arrangement  of  cells,  fibres,  and  vessels  in  the  stem 
of  a  plant  is  co-ordinated  with  those  characteristics  which 
determine  its  position  in  the  evolutionary  series.  We  may 


12  WOOD   PULP  AND  ITS  USES 

briefly  describe  stems  which  are  typical  of  the  two  main 
divisions  of  the  highest  group  of  flowering  plants. 

Fig.  5  represents  a  section  of  the  stem  of  a  mono- 
cotyledon. 

These  structural  types  introduce  the  fundamental  con- 
siderations involved  in  differentiation  of  tissues;  ground 


Jute  (mag.  300). 

FIG.  5c.— Section  of  bast  region  showing  structure  of 
bundles  and  thickening  of  ultimate  fibres. 

tissue,  known  as  parenchyma,  is  made  up  of  thin  naked 
cells  showing  equalit}7  in  their  dimensions,  though  occa- 
sionally elongated.  The  earliest  differentiation  of  the 
ground  tissue  separates  nutritive  cells  from  reproductive 
cells  :  in  the  building  up  of  the  plant  body  we  are  concerned 
with  the  former  only,  and  their  further  specialisation 


THE   STRUCTUEAL  ELEMENTS  OF  WOOD  13 

is  an  adaptation  to  mechanical  and  physical  exigencies 
rather  than  for  vital  purposes.  The  requirements  to  be 
met  are  (1)  for  the  transportation  of  nutritive  matter  from 
the  leaves  where  it  is  manufactured,  as  well  as  of  water 
absorbed  by  the  roots.  Hence  the  provision  of  con- 
ducting tissue — or  mestome ;  (2)  the  plant,  to  maintain 


Flax. 

FIG.  5D. — Section  of  stem  of  Linum  showing  groups  of 
bast  fibres  lying  between  wood  and  cortex. 

its    form,    requires    mechanical    support,   and    tissue    is 
differentiated  into  rigid  structures  known  as  stereome. 

These  features  are  generally  illustrated  in  the  annexed 
figure,  showing  in  section  the  stems  of  two  dicotyledonous 
annuals,  flax  and  jute,  and  of  a  monocotyledonous  annual 
Indian  corn  (Zea  Mais). 


14  WOOD   PULP  AND  ITS  USES 

They  will  be  better  understood  after  dealing  with  the 
more  complex  case  of  the  perennial  stem.  The  forma- 
tion of  wood,  i.e.,  massive  wood,  is  a  process  which  is  con- 
cerned with  the  growth  of  trees,  and  although  the  perennial 
growth  introduces  no  new  structural  elements,  it  does 
present  a  certain  development  of  plan  or  arrangement 


FIG.  6. — Transverse  section  of  stem  of  Lynmanthemum 
(aquatic  plant).  Central  axis  with  xylem  and 
phloem  elements.  Ground  tissue  showing  large 
air  cells  producing  buoyancy,  and  star-shaped  idio- 
blasts. 

beyond  that  of  the  annual  stem.  At  the  outset  we  notice 
there  is  a  contrast  of  the  dicotyl  (or  conifer)  stem  with  the 
monocotyl,  and  since  the  supply  of  wood  pulp  is  at  this 
date  exclusively  drawn  from  wood  of  the  former  types,  we 
must  set  out  their  typical  characteristics  in  some  detail. 
The  apex  of  a  growing  stem  exhibits  an  active  condition 


THE  STRUCTURAL  ELEMENTS   OF  WOOD  15 

of  cell  division  with  a  differentiation  into  definite  regions, 
which  becomes  more  marked  as  we  proceed  downwards. 
In  the  finally  differentiated  stem  these  are  marked  out  as 
(a)  epidermis,  the  external  protective  tissue ;  (b)  the  central 
cylinder,  or  stele,  and  between  them  (c)  the  cortex. 
(Lymnanthemum,  Fig.  6.) 


FIG.  7. — Transverse  longitudinal  section  of  stem  of  Tilia 
Europoea  (Lime  Tree),  showing  bast  fibres  and  ground 
tissue. 

In  the  perennial  stem  the  epidermis  does  not  keep  pace 
with  the  increasing  diameter,  and  the  cortex  becomes  the 
external  protective  tissue  known  as  cork,  with  its  well- 
known  impervious  characteristics.  The  cortex  is  complex 
in  structure. 


16 


WOOD  PULP  AND  ITS  USES 


It  contains  active  chlorophyllic  and  assimilating  tissue, 
and  cells  which  have  a  storage  function  ;  also  well-marked 


FIQ.  8. — Tangential  longitudinal  section  through  the  wood 
elements  of  Tilia  Europoea  (Lime  tree).  From  left  to  right 
a  medullary  ray  is  seen  in  the  row  of  little  cells,  followed 
by  typical  wood  fibres,  spiral  and  pitted  vessels,  and  con- 
nective tissue. 


storage  tissues  known  as  collenchyma,  or  sheathing  tissue, 
and  sclerenchyma,  or  hard  tissue.     The  latter  is,  from  the 


THE  STRUCTURAL  ELEMENTS  OF  WOOD 


17 


present  point  of  view,  the  more  important,  as  it  includes  the 
elongated  thick-walled  cells  known  as  fibres  (Fig.  8).  In 
the  central  cylinder,  or  stele,  the  vascular  tissue  is. 
prominent  (Fig.  7).  There  are  two  well-marked  types  of 
vessels — the  tracheae,  which  are  of  large  diameter,  with 


FIG.  9.— Longitudinal  radial  section  of  Pinus  Sylvestris 
timber  showing  well-developed  bordered  pits  upon 
the  walls  of  the  tracheids.  At  right  angles  to  the 
tracheids  is  a  medullary  ray. 

heavy  walls  variously  modified  in  structure  into  spiral 
bands,  rings,  or  reticulations  (Fig.  8). 

Being  destined  for  water  conduction,  they  are  arranged 
end  to  end  in  a  continuous  longitudinal  series.  In  the 
conifer  stem  there  is  very  large  characteristic  development 
of  the  tracheal-like  tissue  ;  but  the  constituent  vessels  differ 

W.P.  c 


18 


WOOD  PULP  AND  ITS  USES 


from  the  true  tracheae  in  having  tapering  ends,  and  in  not 
being  disposed  in  longitudinal  series. 

These  vessels  are  called  tracheids,  and  they  are  charac- 
terised by  pitted  walls  which,  under  the  microscope,  appear 
as  double  concentric  rings  arranged  in  rows  (Figs.  9  and 
10).  The  second  type  of  vessel  is  the  sieve  tube,  so  called 


FIG.  10. — Tangential  longitudinal  section  of  old  wood 
of  Pinus  showing  tracheids  and  medullary  rays  ;  the 
latter  consist  of  two  or  more  rows  of  cells  arranged 
longitudinally. 

from  the  specially  perforated  area  which  they  develop, 
termed  the  callus  plate.  They  are  concerned  in  the  con- 
duction and  distribution  of  organic  nutrient  matter. 

These  two  types  of  vessels  are  characteristic  respectively 
of  the  xylem  or  wood,  and  phloem  or  bast.  In  the 
dicotyledonous  stem  the  strands  of  xylem  and  phloem, 


THE  STRUCTURAL  ELEMENTS  OF  WOOD  19 

though  separate,  are  organised  together  into  vascular 
bundles.  The  disposition  and  relation  of  these  bundles  are 
the  characteristic  of  the  exogenous  stem. 

They  form  a  centric  system — the  xylem  towards  the 
centre,  the  phloem  towards  the  periphery.  The  paren- 
chyma enclosed  in  the  vascular  cylinder  is  the  pith  or 


FIG.  11  A. — Transverse  section  of  stem  of  Gossy- 
"^       pium  (cotton  plant)  showing  one  annular 
ring  of  xylem  and  phloem  elements  with 
intervening  cambium  layer. 

medulla,  and  its  extensions  outwards  between  the  vascular 
bundles  are  called  pith  or  medullary  rays,  and  act  as 
storage  cells  for  reserve  food  material. 

But  the  most  obvious  feature  of  the  transverse  section 
of  a  forest  tree,  viz.,  the  annual  rings,  remains  to  be 
elucidated. 

In  the  xylem-phloem  bundles  there  is  a  central  portion 

c2 


20  WOOD   PULP  AND   ITS  USES 

of  meristematic  tissue,  which  continues  the  process  of  cell 
division  and  differentiation,  contributing  new  xylem  on  the 
one  side  and  phloem  on  the  other.  And  further,  this  active 
tissue,  known  as  cambium,  extends  from  bundle  to  bundle 
across  the  pith  (rays),  assuming  therefore  a  structural  ring. 
The  annual  accretion  of  new  tissue,  which  is  a  product  of 
the  cambium,  is  thus  marked  as  in  a  ring.  (Fig.  HA.) 

As  the  trunk  or  stem  increases  in  girth,  an  increasing 
portion  of  the  xylem  ceases  to  take  part  in  the  conduction 
of  water,  the  ascending  sap  passes  through  the  younger 
tissues  or  sap  wood,  which  becomes  differentiated  in  colour 
and  other  aspects  from  the  heart  wood ;  in  fact,  it  is  this 
differentiation  of  the  sap  wood  from  the  heart  wood  by 
the  formation  of  vessels,  tracheids,  and  fibres  of  larger 
diameter  and  thinner  walls  in  the  former  tissues,  that  serves 
to  accentuate  the  well-marked  characters  of  the  rings. 
(Fig.  HB.)  The  concentricity  of  the  rings  varies  also  in 
different  trees ;  the  gymnosperms,  for  example,  are  ex- 
tremely regular,  whilst  in  some  angiosperms  the  rings  are 
more  or  less  wavy,  and  in  others  again,  such  as  the  beech, 
the  rings  are  crested.  The  new  phloem  deposited  in  contact 
with  the  old,  causes  rupture  of  the  latter,  and  it  pulls  or 
scales  away  more  or  less  rapidly. 

The  bark  of  trees  is  very  complex  in  structure,  very 
variable  in  character  both  as  regards  its  structural  com- 
ponents and  its  proportion  and  massive  distribution ; 
generally  it  is  not  permanently  associated  with  the  stem  or 
trunk,  as  are  the  new  wood  tissues.  This  is  also  in  accord- 
ance with  our  superficial  observations  of  the  habits  of 
trees. 

The  conspicuous  feature  of  the  dicotyledonous  stem  is, 


THE  STBUCTUKAL  ELEMENTS  OF  WOOD  21 

therefore,  the  collateral  vascular  bundle,  open  in  the  sense 
that  the  cambium  constitutes  a  connecting  tissue  linking 


FIG.  1  IB.— Transverse  section  of  a  three-year- old  stem  of 
Tilia  (Lime  Tree).  At  centre  pith  then  xylem  (wood) 
in  three  separate  rings.  Towards  the  periphery 
the  cambium  ring  then  phloem  and  cortical  tissue. 

the  bundles.     In  contrast  with  this,  the  monocotyledonous 
stem   is    composed    essentially   of   a   ground  tissue,   and 


22  WOOD  PULP  AND  ITS  USES 

scattered  but  closed  fibro-vascular  bundles,  i.e.,  with  no 
connecting  cambium  (see  Fig.  5). 

This  arrangement  implies  an  absence  of  provision  for 
large  increase  of  diameter,  and  the  stem  of  a  perennial  of 
this  type  is  columnar  or  cylindrical  rather  than  conical. 

There  is  a  corresponding  lack  of  provision  for  developing 
an  increase  of  foliage  by  way  of  a  system  of  branches. 
The  foliage  is  thus  a  crown  of  leaves,  as  in  the  palm 


FIG.  12. — Date  Palm.     Typical  Monocotyledon  Perennial. 

(Fig.  12),  which  remains  very  much  the  same  from  year 
to  year.  (Compare  with  Figs.  12s,  12c.)  The  vascular 
bundles  generally  develop  stereome  tissue,  i.e.,  sclerenchy- 
matous  thick-walled  fibres  which,  in  association  with  the 
vessels,  constitute  the  fibres  and  vascular  bundles. 

We  have  now  become  aware  of  the  principal  structural 
elements  of  a  wooded  stem,  and  we  can  analyse  some  of 
the  aspects  of  wood  sections  which  are  familiar  to  us  as 
the  "  grain." 


THE  STRUCTURAL  ELEMENTS  OF  WOOD 


23 


Usually  the  xylem  elements  are  parallel  to  the  axis,  in 
which  case  we  have  the  term  "  straight  grain " ;  but 
irregularities  appear  in  the  growth  of  the  various  tissues 


FIG.  12B. — Pine.     Typical  Conifer.     Exogenous  Gymnosperm. 

(1)  by  a  continuation  of  the  growth  of  the  cells  after  separa- 
tion from  the  cambium  proper,  thus  causing  an  interlacing 
of  the  fibrous  elements,  with  a  consequent  cross-grain 


24  WOOD  PULP  AND  ITS  USES 

effect ;  or  (2)  in  the  formation  of  branches  and  adventitious 
buds,  producing  the  effect  known  as  "  burr."  Other 
irregularities  are  seen  in  the  projections  of  the  xylem 


FIG.  12c. — Oak.     Typical  Angiosperm  Exogenous  Perennial. 

elements  from  the  rings,  causing  the  "  bird's-eye  "  effect  so 
well  marked  in  the  maple. 

In  the  angiosperins  the  medullary  rays  are  much  more 


THE  STRUCTURAL  ELEMENTS  OP  WOOD  25 

highly  developed  than  in  the  gymnosperms,  and  constitute 
in  some  cases  a  large  percentage  of  the  wood. 

In  the  oak  the  primary  medullary  rays  may  be  built  up 
of  several  hundred  rows  of  cells,  and  when  seen  in  radial 
sections  appear  as  silvery  bands,  or  silver  grain,  as  it  is 
termed. 

Some  of  the  poplars  frequently  have  the  medullary 
system  aggregated  together  in  spots  known  as  "  pith 
flecks,"  which  help  to  identify  the  species. 

We  may  note  that  in  addition  to  the  formation  of  the 
ligno-cellulose  or  primary  plant  substance  (see  p.  57),  various 
other  products  of  secretion  are  formed.  Proteins,  or  nitro- 
genous bodies,  carbohydrates,  glucosides,  resins,  and  other 
aromatic  substances,  acids,  such  as  tannic  acid,  dye  stuffs, 
which  impart  particular  characters  to  the  woods,  and  aid  in 
its  identification. 

PHYSICAL  PROPERTIES  OF  WOODS. 

Weight. — This  depends  upon  the  condition  of  the  wood 
in  relation  to  moisture,  and  as  regards  structure,  i.e.,  upon 
the  proportion  of  small  heavily  lignified  vessels  such  as 
would  be  illustrated  by  the  "  heart  wood,"  this  being 
relatively  much  more  dense  than  the  more  distended 
vessels  of  the  "  sap  wood." 

The  following  table  illustrates  the  density  of  various 
woods : — 

Wood.  Density. 

Very  light  Poplar  0'26         0'4 

Light  Spruce  and  Pine     0'4          0'6 

Moderately  heavy       Birch  and  Beech    0*6          0'7 
Heavy  Oak  0*8  and  upwards 


26  WOOD  PULP  AND  ITS  USES 

Hardness. — This  is  usually  measured  in  terms  of  the 
number  of  kilograms  required  to  force  a  punch  of  1  sq.  cm. 
in  area  to  a  depth  of  1*27  mm.  into  the  wood,  perpen- 
dicular to  the  direction  of  the  fibres. 

The  following  table  illustrates  the  relative  hardness  in 
decreasing  proportions  :— 

Hardness  in 

Wood.  kilograms 

per  sq.  cm. 

Lignum  Yitse 793 

Oak          .  ....  225 

Beech 200 

Most  coniferous  woods      ....  100 
Cotton  tree  Boinbax  Malabaricuni 
(type  of  softest  wood) 

Strength  of  Woods. — This  may  be  defined  as  the  resistance 
offered  by  the  wood  to  any  force  tending  to  break  the  fibres 
across  (transverse  stress),  or  to  overcome  the  cohesion  of  the 
fibres  (longitudinal  stress). 

In  the  testing  of  woods  various  other  stresses  are  applied; 
but  the  breaking  strain,  as  stated  above,  is  by  far  the  most 
important. 

It  is  found  that  in  broad-leaved  trees  the  lateral  resistance 
is  from  Jth  to  Jth  of  the  longitudinal  resistance,  and  in 
the  coniferous  ^h  to  j^th. 

Tetmayer  of  Zurich  has  arranged  in  the  following  table 
the  relative  resistance  of  the  woods  to  various  stresses : — 

Transverse 
Pressure.  Tension.  Crushing.  Shearing. 

Beech  Beech  Oak  Beech 

Oak  Oak  Beech  Oak. 


PHYSICAL  PROPERTIES  OF  WOODS  27 


Transverse 
Pressure. 

Larch 

Tension. 
Scotch  Pine 

Crushing. 
Larch 

Shearing. 
Larch 

Silver  Fir 
Spruce 
Scotch  Pine 

Larch 
Spruce 
Silver  Fir 

Silver  Fir 
Spruce 
Scotch  Pine 

Spruce 
Silver  Fir 
Scotch  Pine. 

It  was  found  that  Scotch  pine  had  the  lowest  technical 
value,  silver  fir  20  per  cent,  greater,  spruce  26  per  cent, 
greater,  larch  66  per  cent,  greater,  oak  beech  95  per  cent, 
greater. 

Two  other  factors  usually  determined  in  wood  are  (1)  the 
ash,  that  is  the  amount  of  inorganic  constituents  left  after 
burning  the  wood,  which  is  a  small  proportion  by  weight 
though  voluminous  ;  (2)  the  calorific,  or  fuel,  value  of  the 
wood.  On  an  average  it  is  found  to  be  about  4,000 
calories  or  heat  units,  in  other  words,  one  unit  of  weight 
of  dry  wood  on  burning  furnishes  heat  which  would  raise 
4,000  units  of  weight  of  water  1°  C. 

The  foregoing  brief  expose  implies  the  fundamental  con- 
ditions of  fitness  of  a  given  wood  or  wood  substance  for 
conversion  into  a  fibrous  raw  material.  These  are  primarily 
a  large  proportion  of  elongated  cells  or  fibre,  and,  as  the 
basis  of  economic  production  of  such  pulps,  it  will  be 
obvious  that  the  massive  perennial  stem  fulfils  essential 
industrial  conditions  of  growth,  transport,  and  treatment 
for  conversion  into  pulp,  which  result  in  low  cost  of 
production. 

The  processes  of  pulping  to  be  dealt  with  in  a  subsequent 
chapter,  are  of  two  kinds :  (1)  a  simple  disintegration  by 
wet-grinding,  to  a  "  mechanical  "  pulp.  Such  pulps  are  sub- 
stantially the  original  wood  substance,  deprived  incidentally 


28  WOOD   PULP  AND  ITS  USES 

of  water-soluble  constituents  (see  p.  97) ;  (2)  chemical 
processes  which  attack  the  ligneous  constituents  and  convert 
them  into  soluble  derivatives,  leaving  the  cellulose  which 
preserves  the  form  and  dimensions  of  the  original  fibres 
constituting  a  "  chemical "  pulp  composed  of  the  fibrous 
structural  elements  of  the  wood  in  the  fully  resolved 
condition  (see  p.  120). 

The  number  of  woods  fulfilling  what  is  a  very  exacting 
specification  of  requirements,  is  extremely  limited.  Actually 
the  wood  pulp  industry  is  based  upon  the  utilisation  of 
coniferous  woods  and  poplar. 


CHAPTER  II 

I.  CELLULOSE  AS  A  CHEMICAL  INDIVIDUAL  AND  TYPICAL  COLLOID. 
II.  THE  LIGNONE  COMPLEX,  LIGNO-CELLULOSE ;  SPECIAL 
CHEMICAL  NOTE  ON  AUTOXIDATION,  AND  RESEARCHES  OF 
W.  J.  RUSSELL 

THE  investigation  of  the  nature  and  composition  of  the 
woods  is  a  problem  of  "  organic  chemistry."  The  wood 
substance  is  in  all  cases  a  complex  of  carbon  compounds. 
The  woods  present  variations  in  composition  which  are 
definite  and  characteristic ;  but  these  are  only  minor 
divergences  from  a  common  type.  As  representative  of 
the  type  we  may  take  two  individuals. 

The  jute  fibre— the  lignified  bast  fibre  of  an  annual,  a 
simple  tissue — and  beech-wood,  which  represents  perennial 
growth,  and  from  its  nature  is  an  assemblage  or  mixture  of 
structural  elements. 

We  have  in  the  previous  chapter  spoken  of  "  lignification  " 
as  a  process.  Morphologically  it  is  a  process  of  thickening 
by  incrustation,  and  according  to  recent  researches  this 
incrustation  is  a  process  of  forming  adsorption  com- 
pounds, the  colloidal  hydrated  celluloses  first  elaborated, 
taking  up  soluble  colloidal  products  from  solution  in  the 
cambium  fluids  or  "  sap  "  (H.  Wislicenus,  Zcitsch.  Kolloide, 
1910,  p.  17) ;  chemically  it  is  regarded  as  the  formation  of  a 
cellulose  derivative  by  combination  of  cellulose  with 
certain  acid  and  unsaturated  ketonic  groups,  the  resulting 


30  WOOD   PULP   AND   ITS   USES 

compound  or  complex  being  a  ligno -cellulose.  Conversely, 
by  various  processes  which  attack  these  acid  and  unsaturated 
groups,  the  ligno-cellulose  is  resolved  into  derivatives  of  the 
latter  which  are  soluble,  and  cellulose  which  is  resistant 
and  insoluble.  The  separation  or  isolation  of  cellulose  is 
attended  by  disintegration;  the  aggregated  structure  is 
resolved  into  its  component  units,  which  are  cells,  including 
in  this  general  term  fibres  and  vessels.  In  the  ligno- 
celluloses  these  are  of  small  dimensions,  2 — 3  mm.  in 
length,  and  '02 — *03  diameter.  A  mass  of  such  units  in 
contact  with  water  constitutes  a  "  pulp."  The  separated 
cells  retain  their  dimensions  and  general  structural 
characteristics  notwithstanding  that  the  elimination  of  the 
non-cellulose  components  is  attended  by  considerable  loss 
of  substance,  i.e.,  weight,  and  the  cellulose  may  therefore 
be  regarded  as  the  more  permanent  skeleton  or  framework 
of  the  cell.  The  quantitative  relations  of  this  resolution 
are  of  importance.  The  following  percentage  numbers 
characterise  the  typical  ligno-celluloses  : — 

Cellulose.  Lignone. 

Jute    .         .         .         70—80       .         .         30—20 
Beechwood  .         50—60       .         .         50—40 

It  may  assist  the  student  in  estimating  the  practical 
significance  of  these  chemical  facts  to  point  out  that  a 
ligno-cellulose  is  related  to  cellulose  somewhat  in  the  same 
way  as  an  alloy  of  gold  with  baser  metals  is  to  gold.  Gold  as 
a  "noble  metal"  is  relatively  non-reactive,  and  especially 
distinguished  by  resistance  to  oxygen,  and  is  therefore 
permanent  in  the  air  and  generally  unaffected  by  the 
conditions  which  prevail  on  the  earth's  surface.  Cellulose 


CELLULOSE  AS  A  CHEMICAL  INDIVIDUAL  31 

is  resistant  to  oxygen  and  water,  and  is  permanent  under 
the  prevailing  conditions  of  our  planet.  A  gold  alloy  is 
amenable  to  the  attack  of  oxygen  which  combines  with  the 
constituent  metals,  converting  them  into  oxides,  or  of 
reagents  which  dissolve  the  baser  metals  as  salts :  the  gold 
is  left  as  elementary  metal.  Similarly,  cellulose  is  obtained 
as  a  residue  resisting  the  action  of  reagents  such  as  chlorine, 
caustic  alkalis  or  bisulphites,  all  of  which  combine 
directly  with  the  lignone  groups,  for  reasons  which  will 
appear. 

It  would  take  us  outside  the  scope  of  our  present  treat- 
ment of  the  subject  to  attempt  an  exhaustive  expose  of  the 
chemistry  of  these  natural  products.  The  special  outline 
which  we  give  may  be  regarded  as  the  irreducible  minimum 
necessary  as  the  foundation  of  the  chemical  technology  of 
the  subject.  We  have  already  implied  that  the  woods  are 
modified  celluloses,  from  which  their  more  important 
constituent,  that  is  the  cellulose,  is  readily  isolated. 

Cellulose  is  a  carbohydrate  ;  it  is  derived  from  the  sugars 
and  under  severe  treatment  may  be  resolved  into  sugars. 
Its  ultimate  composition  is  represented  by  the  formula 
,  and,  in  breaking  down  to  the  simplest  sugar, 
the  process  may  be  formulated  as  one  of  simple 
"  hydrolysis  "  :  7i(C6Hi005)  +  rcH20  =  «C6H1206.  But  of 
the  mechanism  of  this  resolution  we  are  profoundly 
ignorant.  Indeed,  it  cannot  be  said  that  the  above  equation 
of  hydrolysis  has  been  verified  experimentally.  Kecent 
researches  of  H.  Ost  and  L.  Wilkening  (Chem.  Zeit., 
1910,  84,  461),  establish  a  conversion  of  cellulose  into 
fermentable  sugars  to  the  extent  of  90  per  cent,  of  its 
weight,  with  a  residue  of  acid  products.  The  above  equation 


32  WOOD  PULP  AND   ITS  USES 

is  therefore  not  more  than  an  approximate  picture  of  the 
underlying  facts.  This  is  equivalent  to  the  statement  that 
we  are  entirely  ignorant  of  the  actual  constitution  of 
cellulose. 

We  are  more  familiar  with  another  complex  carbohydrate, 
starch,  which  has  a  similar  empirical  formula  w(C6Hi005). 
Starch  is  quantitatively  resolved  into  the  sugars,  maltose 
and  dextrose,  by  hydrolytic  actiOB  determined  by  reagents 
or  by  ferment  actions  and  under  conditions  which  enable 
us  to  follow  minutely  the  stages  of  the  transformation. 
These  reveal  the  extreme  complexity  of  the  aggregate  which 
constitutes  starch.  But  although  we  can  closely  follow  this 
chemical  disintegration  through  its  stages,  we  are  unable  to 
integrate  these  results  of  analysis  into  a  formula,  still  less 
by  any  laboratory  process  to  reascend  the  scale  and  trans- 
form the  products  of  resolution  back  to  starch.  A  fortiori, 
the  proximate  constitution  of  cellulose  is  problematical. 

Starch  and  cellulose  are  not  only  closely  linked  by  many 
analogies  which  have  been  established  by  comparative 
investigation  in  the  laboratory,  but  in  the  plant  they  stand 
in  intimate,  in  fact  genetic,  relationship,  as  evidenced  by 
the  transformation  from  one  to  another,  and  the  equivalence 
of  their  vital  functions  in  many  respects.  Premising  these 
relationships,  we  may  state  that  the  ultimate  component 
groups  of  cellulose  are  those  of  the  carbohydrates  generally 
and  of  the  sugars  in  particular — i.e.,  saturated  compounds 
and  derivatives  of  polyhydric  alcohols — generally  resistant 
i.e.,  non-reactive.  But  the  special  chemistry  of  cellulose 
has  to  do  with  the  complex  or  aggregate.  The  particular 
feature  of  cellulose  is  that  it  enters  into  a  number  of 
reactions,  combining  with  other  bodies  to  form  highly 


CELLULOSE   AS  A  CHEMICAL  INDIVIDUAL          33 

characteristic  derivatives,  in  which  the  essential  properties 
of  the  aggregate  are  fully  maintained.  These  properties 
are  recognised  in  the  following  :  (a)  the  colloidal  character- 
istics of  the  solutions  of  the  original  cellulose,  as  of  its 
ethereal  derivatives  ;  (b)  the  structural  characteristics  of 
the  solids  obtainable  from  these  solutions  by  elimination  of 
the  solvent ;  (c)  the  weight  relations  of  the  products,  the 
cellulose  maintaining  its  integrity  as  a  complex.  What  we 
have  to  set  forth  as  a  Sketch  of  the  special  properties  of 
cellulose  will  follow  this  order  of  idea. 

I. 

Cellulose  as  a  Typical  Colloid. — It  may  be  said  generally 
that  we  know  very  little  of  solid  substances ;  it  is  only  in 
solution  or  the  fluid  state  that  matter  lends  itself  to  quanti- 
tative analytical  investigation.  It  is  in  the  manifestation 
of  associated  properties  in  solution  that  compound  matter 
has  come  to  be  regarded  as  falling  into  two  great  divisions, 
Crystalloids  and  Colloids.  Crystalloids  are  crystalline  as 
solids  and  when  dissolved  in  neutral  solvents  constitute 
limpid  solutions ;  Colloids  are  non-crystalline  or  amorphous, 
and  dissolve  to  viscous  or  gelatinous  solutions.  On  evapo- 
rating the  solvent  the  former  resume  their  crystalline  form, 
the  latter  constitute  structureless  masses ;  these  may  be 
transparent,  and  if  spread  over  a  relatively  large  superficial 
area  they  take  the  form  of  a  film  or  sheet.  A  familiar  type 
of  colloid  is  gelatin.  Gelatin  in  10—20  per  cent,  aqueous 
solution  at  temperatures  of  50—100°,  is  a  viscous  liquid ; 
the  solution  on  cooling  to  20—30°  solidifies  to  a  jelly  or 
"  gel."  The  "  gel  "  continues  to  lose  water  at  its  surface 
and,  by  withdrawing  water  from  the  interior,  continues  the 
process  of  desiccation.  The  "  air  dry  "  solid  finally  retains 

W.P.  D 


34  WOOD  PULP  AND  ITS  USES 

15  per  cent,  of  its  weight  of  moisture,  which  requires  a 
higher  temperature  for  its  expulsion.  The  dry  solid  is 
relatively  inelastic  or  brittle. 

There  are  various  views  current  as  to  the  causes  under- 
lying these  phenomena.  Any  such  view  or  "  theory  of  the 
colloidal  state  "  must  set  out  from  the  observed  experimental 
facts  which  are,  chiefly :  (1)  The  antithesis  between  solid 
crystalline  and  amorphous  matter ;  (2)  the  correlatively 
divergent  properties  of  these  two  types  of  matter  when  in 
solution :  thus,  the  crystalloids  are  generally  electrolytes  : 
they  are  conductors  of  the  electric  current,  by  which  they 
are  readily  decomposed,  taking  up  the  electrical  energy  and 
splitting  into  polar  constituents  ;  the  colloids  are  non-con- 
ductors in  this  sense.  The  crystalloids  are  diffusible,  i.e., 
they  readily  pass  through  membranes  such  as  parchment, 
or  parchmentised  paper — the  phenomena  being  classified 
under  the  term  osmosis ;  the  colloids  are  not  diffusible — 
that  is,  exert  no  osmotic  pressure  in  solution — and  conse- 
quently are  not  transmitted  through  such  membranes  or 
films. 

The  crystalloids,  in  dissolving,  undergo  changes  of  volume, 
accompanied  by  considerable  thermal  effects :  the  colloids 
dissolve  with  relatively  slight  volume  change.  Colloidal 
matter,  when  observed  in  transparent  forms,  is  optically 
homogeneous ;  crystalline  matter  exhibits  selective  actions 
which  are  classified  under  the  term  polarisation.  These 
effects  in  certain  groups  of  compounds,  e.g.,  the  sugars, 
persist  in  their  solutions.  It  is  important  to  note  that  we 
have  the  primary  antithesis  of  solid  form,  associated  with 
differentiated  relationships  to  the  various  forms  of  energy — 
electricity,  heat  and  light.  It  must  not  be  assumed,  how- 
ever, that  there  is  any  sharp  distinction  of  one  form  of 


CELLULOSE  AS  A  CHEMICAL   INDIVIDUAL  35 

matter  from  another  :  the  antithesis  is  an  opposition  of 
extremes,  emphasised  by  the  comparison  of  typical  repre- 
sentatives. But  these  extremes  graduate  on  either  side 
into  forms  of  matter  which  have  the  characteristics  of  both. 
There  is  an  important  deduction  from  these  relationships, 
which  is  that  throughout  the  series  the  ultimate  properties 
of  matter  are  involved  as  the  conditioning  factor  of  the 
"  physical  "  state.  It  was  formerly  held  that  the  antithesis 
of  crystalloid  and  colloid  was  of  "  physical "  significance 
only,  that  is,  depended  rather  upon  proximate  relationships 
than  upon  the  ultimate  properties  of  matter,  which  are 
"  chemical."  We  cannot  pursue  this  theme  at  any  length, 
and  we  must  refer  students  who  aim  at  more  fundamental 
analysis  of  phenomena  to  special  treatises,  instancing  more 
particularly  "  Neue  Gesichtspunkte  zur  Theorie  der  Kol- 
loide  "  (E.  Jordis,  Erlangen,  1904),  and  other  critical  and 
experimental  contributions  which  connect  the  properties  of 
colloids  with  the  modern  theory  of  solutions.  As  a  general 
text  book  we  need  only  mention  "  Grundriss  der  Kolloid- 
chemie,"  by  W.  Ostwald  (Dresden,  T.  Steinkopff).  For  a 
general  resume  of  the  literature  of  colloids  covering  the 
earlier  periods,  the  "  Bibliographic  der  Kolloide,"  by 
A.  Miiller  (Leipzig,  1904,  L.  Yoss),  and  for  present  develop- 
ments the  scientific  serial  "  Zeitschrift  fiir  Chemie  und 
Industrie  der  Kolloide  "  (Dresden,  Steinkopff).  As  a 
general  review  of  the  chemistry  of  cellulose  considered  as 
a  typical  colloid  and  tlie  probable  relationships  of  its 
colloidal  characteristics  to  chemical  constitution,  the 
student  may  consult  "Researches  on  Cellulose,"  II.  (1906), 
Cross  and  Bevan. 

Cellulose  is  itself  insoluble  in  all  neutral  solvent  liquids. 

D2 


36  WOOD   PULP  AND   ITS  USES 

The  "  solutions  of  cellulose  "  are  in  all  cases  solutions  of 
derivatives.  There  are  two  main  groups  of  these  deriva- 
tives :— 

(a.)  Colloidal  double  salts  of  cellulose  with  metallic  saline 
compounds,  viz.,  zinc  chloride  and  cuprammonium.  A 
"  solution  of  cellulose  "  results  from  digestion  with  these 
reagents  in  aqueous  solution,  and  the  cellulose  is  separated 
from  these  solutions  by  mere  dilution.  It  is  obtained  in 
a  gelatinous,  hydrated,  and  of  course,  structureless  form. 
The  precipitated  cellulose  retains  the  metallic  oxides ;  but 
these  are  readily  removed  by  treatment  with  acids.  The 
solutions  have  a  high  viscosity  and  the  limit  of  fluidity,  for 
the  purpose  of  the  practical  applications  of  these  solutions 
is  reached  when  the  percentage  of  cellulose  in  solution  is 
5 — 7.  Higher  percentages  in  fluid  solution  are  attained  at 
the  expense  of  the  integrity  of  the  cellulose  aggregate,  that 
is,  by  various  processes  of  hydrolysis ;  thus,  by  employing 
with  the  zinc  chloride  various  and  increasing  proportions 
of  hydrochloric  acid,  or  by  previous  treatment  of  the 
cellulose  with  both  acid  and  basic  reagents,  which  resolve 
the  aggregate  by  hydrolytic  actions.  It  must  be  noted  that 
the  state  of  disintegration  of  the  aggregate  persists  in  the 
reverted  product ;  the  cellulose  recovered  from  the  solutions 
by  precipitation  is  more  or  less  degraded  in  its  structural 
properties. 

(b.)  The  esters  of  cellulose  are  the  derivatives  which 
result  from  the  combination  of  its  OH  groups  with  acid 
radicals.  The  most  important  of  these  are  the  Nitrates,  or 
so-called  Nitrocelluloses,  the  Acetates  and  Benzoates.  The 
Benzoates  are  of  no  practical  (i.e.,  industrial)  importance. 
The  Nitrates  and  Acetates  are  formed  by  the  action  of  the 


CELLULOSE   AS  A   CHEMICAL  INDIVIDUAL  37 

acids  or  their  anhydrides  upon  cellulose.  The  "  nitration  " 
or  "  acetylation  "  is  progressive,  and  to  form  derivatives 
soluble  in  various  neutral  liquids  the  degree  of  esterification 
must  proceed  beyond  a  certain  limit,  viz.,  that  represented 
by  the  combination  of  two  of  the  OH  groups  of  the  unit 
CeHioOs-  Actually  the  derivatives  most  commonly  employed 
are,  in  the  case  of  the  nitrates,  the  esters  intermediate 
between  the  dinitrate  and  trinitrate  ;  in  the  case  of  the 
acetates,  the  complete  solubility  of  the  ester  requires  a 
stage  of  esterification  closely  approximating  to  the  produc- 
tion of  a  triacetate. 

The  solvents  employed  are  in  the  case  of  the  nitrates, 
ether-alcohol,  alcohol  and  camphor,  ethyl-acetate,  ace- 
tone, and  variations  of  these.  The  acetates  are  soluble  in 
a  more  limited  range  of  liquids,  of  which  chloroform  is  the 
most  important  and  characteristic ;  other  solvents  are 
acetic  acid,  phenol,  and  pyridine.  It  is  important  to  note 
that  these  esters  are  produced  with  a  necessarily  large 
increase  of  weight  of  the  product  as  compared  with  the 
original  cellulose,  resulting  from  the  introduction  of  the 
relatively  heavy  acid  or  negative  group.  This  will  be 
appreciated  from  inspection  of  the  equations  representing 
the  limiting  reactions  thus  :— 

Cellulose.  Nitric  Acid.  Water.  Cellulose  Trinitrate. 

C6Hio05      +     3  HN03     =      3  H20     +     C6H702  (N03)3 
162  (3  X  63)         (3  X  18)  297 

Cellulose.        Acetic  Acid.  Cellulose  Triacetate. 

5  +  3  C2H402     =     3  H20  +  C6H702  3  (C2H302) 
162  (3  x  60)  (3  x  18)  288 


38  WOOD    PULP  AND   ITS  USES 

an  increase  of  weight  in  either  case  of  over  75  per  100  of 
cellulose. 

These  combinations,  involving  such  large  increases  of 
weight,  may  take  place  under  regulated  conditions,  without 
affecting  the  structural  integrity  of  the  fibre ;  the  esters 
differing  but  little  in  external  appearance  from  the  original 
cellulose. 

They  now  dissolve  in  their  respective  solvents  to 
structureless  solutions,  which  are  fluid  at  concentrations  of 
10 — 15  per  cent,  of  the  ester.  It  is  to  be  noted  from  the 
weight  relationship  above  set  forth  that  these  concentrations 
are  in  their  equivalent  of  cellulose  6 — 8  per  cent. 

From  these  solutions  the  esters  are  recovered  unchanged, 
by  evaporation  of  the  solvent,  or  by  removing  it  by  the 
action  of  a  liquid,  which  mixes  with  the  solvent  but  is  not  a 
solvent  of  the  cellulose.  From  the  esters  so  recovered,  the 
cellulose  can  only  be  regenerated  by  the  chemical  process 
of  saponification,  that  is,  by  the  attack  of  certain  alkaline 
agents  which  combine  with  and  remove  the  combined  acid 
groups  and  restore  the  OH  groups  of  the  original  cellulose. 

In  the  industrial  uses  of  these  compounds  they  are 
sometimes  employed  as  such,  or  as  in  the  production  of 
artificial  silk,  the  solution  being  drawn  or  spun  through 
fine  orifices  and  solidified  to  the  artificial  thread  which  in 
the  case  of  the  nitrate  is  then  denitrated  or  saponified  to 
cellulose. 

The  industrial  process  is  therefore  in  the  latter  case  a 
complete  chemical  cycle ;  the  ester  stage  being,  for  all 
practical  purposes,  merely  a  solvent-plastic  condition  of  the 
cellulose. 

(c.)  Intermediate  between  these  two  groups  and  combining 


CELLULOSE   AS  A  CHEMICAL   INDIVIDUAL  39 

their  essential  features,  is  the  derivative  known  as  the 
sulpho-carbonate,  or  in  solution,  as  viscose.  This  is  a 
water-soluble  ester  of  cellulose,  formed  by  treating  cellulose 
with  strong  solutions  of  the  alkaline  hydrates,  e.g.,  caustic 
soda,  and  the  compound  so  obtained,  or  alkali-cellulose  with 
carbon  bi-sulphide.  The  ester  is  thus  synthesised  in  the 
two  stages,  and  its  final  form  is  the  sodium  salt  of  cellulose- 
xanthogenic  acid,  a  compound  freely  soluble  in  water. 
The  aqueous  solutions  of  these  derivatives  (viscose)  are 
structureless,  and  at  cellulose  concentrations  of  8 — 12  per 
cent.,  are  sufficiently  fluid  for  manipulation  through  filters 
and  for  passage  through  fine  orifices  under  small  pressures. 
(See  p.  247.) 

The  reaction  which  produces  these  compounds  is  a 
reversible  one,  and  the  solutions,  on  standing,  spontaneously 
revert  to  cellulose  by  dissociation  of  the  alkaline  sulphur 
residues.  The  cycle  of  synthesis  and  decomposition  may 
be  represented  by  the  subjoined  diagram  :— 

Synthesis. 

«i  Alkaline  hydrate  Solution  of 

Cellulose  — >  Xanthogenic  Ester. 

Carbon  Bisulphide  / 

Viscose. 


-  Carbon-disulphide 

Alkali  and  products  of  and  Cellulose  (Hydrate) 

\     interaction 

Upon   these  fundamental   facts   are    based   a   number   of 
important  industrial  applications  of  cellulose. 


40  WOOD  PULP  AND  ITS  USES 

In  the  preceding  section  we  have  indicated  that  the 
cellulose  in  the  form  of  these  soluble  derivatives  is  a 
structureless  colloid.  In  the  plastic  condition  it  may  be 
made  to  take  any  desired  form,  and  it  is  produced  indus- 
trially in  filament  or  thread,  in  film  or  sheet,  or,  lastly,  in 
massive  solids  of  any  required  dimensions.  The  special 
feature  of  these  artificial  forms  is  a  particular  continuity  of 
substance.  In  passing  from  the  state  of  solution  to  the 
ultimate  solid  form  there  are  no  breaks  in  this  continuity, 
and  the  structural  characteristics  of  these  artificial  forms 
are  conditioned  by  this  fact,  which,  in  turn,  rests  upon  the 
ultimate  constitution  of  the  cellulose  substance  or  matter. 
This  finally  must  be  held  to  be  intimately  associated  with 
its  typically  colloidal  properties. 

The  practical  effects  or  consequences  of  these  constitu- 
tional properties  are  seen  in  the  qualities  of  resistance  of 
the  derivative  solids.  The  mechanical  properties  of  the 
artificial  threads,  which  are  expressed  in  terms  of  tensile 
strength  or  tenacity,  extensibility  (elasticity),  are  essential 
factors  of  their  textile  applications.  These  properties  are 
compared  and  brought  to  numerical  expression  in  various 
ways :  thus  the  tenacity  is  measured  in  terms  of  the 
maximum  weight  which  the  thread  will  support.  As  an 
average  figure  we  may  take  this  as  8,000 — 9,000  grms. 
per  square  millimetre  of  section.  Another  mode  of 
expression  of  the  physical  fact  is  in  terms  of  "breaking 
length,"  that  is,  the  length  of  the  particular  fabric  repre- 
senting such  breaking  weight.  Elasticity  is  the  maximum 
elongation  of  the  thread  under  strain  from  which  it  will 
revert  to  its  original  dimensions  when  the  strain  is 
removed.  This  may  be  2  to  3  per  cent.  Extensibility  is 


CELLULOSE  AS  A  CHEMICAL  INDIVIDUAL          41 

the  elongation  of  the  thread  when  strained  to  its  breaking 
point.  This  varies  from  10  to  20  per  cent.1  These  cellulose 
threads  are  known  as  "  artificial  silks,"  and  it  is  evident 
from  the  term,  that  they  are  applied  to  similar  purposes  as 
the  natural  silks.  It  is  of  interest,  therefore,  to  compare 
these  products  in  regard  to  their  fundamental  mechanical 
properties.  We  quote  from  a  paper  on  "  Cellulose  and 
Chemical  Industry"  (Cross  and  Bevan,  Journ.  Soc.  Chem. 
Iml,  27,  1908). 

The  comparison  with  silk  is  direct  and  simple,  since  both 
represent  amorphous  colloidal  matter  or  substance. 

The  artificial  silks  may  be  taken  as  showing  the  following 
range  of  textile  quality  :— 

Gramme. 

2  Breaking  strain  or  tenacity  per  unit  denier     .  1*0 — 1*4 

Extensibility  under  breaking  strain           .         .       13% — 17% 
True  elasticity   . 4%—  5% 

The  corresponding  averages  for  the  true  silks  (in  the 
boiled-off  state)  are:— 

Breaking  strain  or  tenacity  per  denier       .         .  2'0 — 2-5 

Extensibility  under  breaking  strain  .         .         .         15% — 25% 
True  elasticity 4%— 5% 

Strehlenert  has  established  the  following  relationships, 
which  are  important  (Chem.-Zeit.,  1901,  p.  1100). 

The  breaking  lengths  are  expressed  in  terms  of  kilo- 
grammes per  square  millimetre  of  section,  which  is  a 


1  These  points  are  further  elucidated  in  Chap.  X. 

2  Denier  is  the  unit  weight/length  :  mgr.  per  10  metres. 


Natural 
silk." 


42  WOOD  PULP  AND  ITS  USES 

satisfactory   basis    of    comparison    in    view  of    the   close 
structural  similarity  of  the  products  investigated  :— 

Dry  Wet. 

'China  raw  silk 53'2  46'7 

French,,     ,, 50-4  40'9 

„       boiled  off  .....  25-5  13'6 

„       dyed  red,  weighted     .                  .  20'0  15*6 

„       blue  black  at  110  per  cent.         .  12-1  8-0 

,,         „  140  per  cent.         .  7'9  6-3 

,,          ,,         ,,  500  per  cent.           .  2'2 

"Artificial  (  Chardonnet     ),-,..  (         14*7  1'7 

.,,     ,,        T   ,  [  Nitrate  process       .        \ 

silks.       J  Lehner  j  17*1          4'8 

Lustra      j  Glanzstoff,  cuprammoniuu)  process        .         19'1  3'2 

celluloses    (  Viscose,  xanthate  process        .         .         .         21'5  5*3 

The  lustra  celluloses  are  thus  inferior  in  tenacity  to 
the  silks,  but  when  these  are  "  weighted "  there  is  a 
loss  of  strength  beyond  that  which  would  be  directly 
proportional  to  the  degree  of  "  dilution "  of  the  silk 
substance, 

As  the  weighting  of  silks  is  very  largely  practised,  it 
will  be  seen  that  the  lustra  celluloses  are  quite  on  the 
average  level  of  textile  quality,  even  in  this  higher 
sphere. 

In  regard  to  elasticity  and  extensibility,  which  are 
important  correlative  measures  of  textile  quality,  a  similar 
series  of  relations  obtains. 

The  lustra  celluloses,  on  the  other  hand,  have  a  special 
relationship  to  water,  the  colloidal  cellulose  having  a  con- 
siderable hydration  capacity.  In  actual  practice  this  fact 
is  not  of  such  moment  as  to  impede  the  very  rapid  progress 
of  the  industry  in  these  new  textiles. 

That  this  property  or  relationship  of  the  cellulose  is 
modifiable  appears  to  be  a  reasonable  deduction  from  the 


CELLULOSE  AS  A  CHEMICAL   INDIVIDUAL  43 

general  reactivity  of  cellulose.  It  has  been  presumed  by 
investigators  that  the  cellulose  (hydrate)  is  susceptible  of 
modification,  either  by  intrinsic  or  constitutional  change, 
or  by  reaction  to  form  a  new  derivative,  in  such  a  way  as  to 
yield  a  product  more  nearly  resembling  the  normal  cotton 
cellulose  in  resistance  to  hydration.  At  this  date  there  is 
only  one  method  which  has  given  promise  of  industrial 
results  in  this  desirable  direction. 

The  cellulose,  notably  in  the  form  of  artificial  silk,  is 
treated  with  formaldehyde  in  aqueous  solution  containing 
also  auxiliary  agents  determining  combination. 

As  a  result  of  the  combination  it  appears  there  is  some 
constitutional  change  in  the  cellulose  itself  accompanying 
the  fixation  of  the  H2CO  groups,  and  this  suggestion  is  of 
moment,  as  it  indicates  a  capacity  of  internal  structural 
modification  which  offers  an  attractive  field  for  research. 

It  is  of  particular  interest  to  note  that  the  artificial  silks, 
though  produced  by  treatments  of  cellulose  presenting  the 
widest  contrasts  in  chemical  and  physical  conditions,  are 
closely  similar  in  their  properties.  It  is  evident  from  this 
that  though  cellulose  is,  in  chemical  language,  extremely 
labile,  it  is  nevertheless  so  constituted  as  an  aggregate  as 
to  be  equally  stable,  or  resistant  to  change. 

The  reversion  of  cellulose  or  of  its  esters  from  the 
solutions  above  enumerated,  in  the  form  of  film  or  sheet, 
introduces  no  novel  features  of  the  product.  The  qualities 
of  the  film  which  condition  its  industrial  employment  are 
tensile  strength  and  elasticity. 

In  the  production  of  solids  in  massive  forms,  a  number  of 
factors  are  introduced  with  the  exaggeration  of  the  third 
dimension,  and  only  one  of  the  solutions,  viz.,  viscose, 


44  WOOD   riJLP  AND   ITS  USES 

lends  itself  to  the  production  of  cellulose  products  of  this 
order.  The  nitrate  solutions  which  are  the  basis  of  the 
highly  important  celluloid  industry  are  a  plastic  form  of  the 
nitrate  or  cellulose  ester,  and  the  forms  into  which  it  is 
fashioned  while  in  the  plastic  state  are  but  little  different  in 
dimensions  from  those  of  the  permanent  and  rigid  solids 
into  which  they  pass  by  evaporation  of  the  solvent. 
These  are  constituted  of  the  unchanged  nitrate  or  cellulose 
ester.  No  economical  method  has  been  devised  for  turning 
out  the  acid  groups  from  the  ester  in  these  massive  forms 
and  thus  arriving  at  cellulose  in  corresponding  forms.  But 
the  viscose  solutions  in  spontaneously  reverting  to  cellulose 
and  solidifying  may  be  cast,  at  this  stage,  into  any  desired 
form.  The  masses  so  obtained  are  composed  of  the  cellulose 
in  a  much  hydrated  state  ;  but  though  retaining  nine  times 
its  weight  of  water  (of  hydration)  it  has,  nevertheless,  a  con- 
siderable mechanical  resistance.  Permeated  as  it  is  with 
the  alkaline-sulphur  by-products,  it  requires  exhaustive 
washing  to  remove  them.  The  purified  mass  of  hydrated 
cellulose,  if  now  dehydrated  and  desiccated  by  exposure  to 
the  atmosphere,  parts  with  its  water  continuously  and 
progressively,  shrinks  upon  itself,  and  finally,  is  obtained 
in  transparent  or  translucent  masses.  The  cellulose  solid 
so  obtained  is  an  extremely  resistant  material. 

The  properties  of  this  material  may  be  compared  with 
those  of  other  solids  used  in  construction,  and  it  will  be  seen 
to  have  qualities  of  a  very  high  order. 

Lastly,  we  have  to  call  particular  attention  to  the 
facts  which  have  been  generally  noted  as  regards  the 
weight  relationships  of  these  cycles  of  transformations. 
Taking  the  two  extreme  cases,  that  is,  with  the  widest 


CELLULOSE   AS  A  CHEMICAL   INDIVIDUAL  45 

divergence  of  the  conditions  of  reaction  and  with  reference 
to  the  same  unit  of  cellulose,  which  we  may  conveniently 
take  at  100  parts  by  weight : 

Cycle  a.     Cellulose.     Nitrate.     Cellulose  (hydrate}  Acid. 

One  hundred  parts  of  cellulose  combine  with  nitric  acid 
(with  elimination  of  water)  becoming  165  parts  of  cellulose 
nitrate,  dissolved  in  alcohol-ether  to  15  per  cent,  solution 
(equivalent  to  9  per  cent,  cellulose)  and  spun  to  thread, 
denitrated  with  ammonium-magnesium  sulphydrate,  and 
reverting  to  103  parts  by  weight  of  cellulose  hydrate. 

Cycle  |3.  Cellulose.     Xanthogenic  Ester.     Cellulose  hydrate. 

Alkaline. 

One  hundred  parts  of  cellulose  combine  with  50  parts 
sodium  hydrate  (in  presence  of  water),  the  alkali  cellu- 
lose reacts  with  50  parts  disulphide,  giving  130  parts  of 
cellulose-xanthate  of  soda  dissolved  to  13  per  cent, 
solution,  equivalent  to  10  per  cent,  cellulose,  drawn  or  spun 
into  "  setting  "  solutions  (see  p.  246),  which  decompose  the 
ester  and  regenerate  cellulose,  yielding  103  parts  by  weight 
of  cellulose  (hydrate). 

In  either  case,  therefore,  the  cycle  is  completed  without 
loss  of  substance  by  the  cellulose :  there  is  a  slight  gain 
due  to  combination  with  water. 

This  is  only  strictly  true  of  the  normal  cellulose,  which 
is  represented  by  the  fully  purified  cotton  fibre.  Other 
celluloses,  notably  wood-celluloses,  sustain  a  loss  of  weight 
due  to  conversion  into  permanently  soluble  derivatives, 
which  may  amount  to  10 — 20  per  cent.  Keciprocally,  the 


46  WOOD  PULP  AND  ITS  USES 

viscose  cycle  becomes  a  constitutional  criterion,  a  normal 
cellulose  being  one  which  sustains  this  cycle  of  reactions  of 
synthesis  and  decomposition  without  loss  of  substance. 

These  experimental  facts  define  cellulose  as  a  typical 
colloid.  It  has,  of  course,  long  been  recognised  in  general 
terms  that  cellulose  in  its  "  organic  "  forms  must  be  classi- 
fied as  a  colloid.  But  the  colloidal  state  having  become  a 
definite  objective  of  investigation,  it  is  evident  that  the 
investigation  of  cellulose  through  its  compounds  and  deri- 
vatives is  destined  to  contribute  considerably  to  the  develop- 
ment of  the  general  theory  of  the  colloidal  state.  For  this 
reason,  added  to  the  fact  that  all  the  industrial  applications 
of  cellulose  specially  involve  its  colloidal  characteristics,  we 
have  limited  our  present  treatment  of  the  subject  to  this 
particular  aspect. 

We  now  give  a  brief  systematic  resume  of  the  properties 
of  cellulose  as  a  chemical  individual,  these  tyyical  charac- 
teristics being  those  of  cotton  cellulose. 

CELLULOSE.  —  Generally  the  non-nitrogenous  skeleton  of 
vegetable  tissues.  Type  :  the  fibre-substance  of  cotton, 
purified  from  associated  "impurities"  by  processes  of  (1) 
alkaline  hydrolysis  and  oxidation  (bleaching)  ;  (2)  of 
digestion  with  hydrofluoric  acid,  etc.,  to  remove  mineral 
impurity. 

(0-44*\ 

Composition.  —  Elementary    j  H   6*2  ?  whence  the  empiri- 

V  049-4/ 
cal  formula 


Constitution  undetermined.     Is  variously  regarded  as  : 

Air]  OQA  *   " 

(1)  Polyhexose  (anhydride)<Ketose' 


CELLULOSE  AS  A  CHEMICAL  INDIVIDUAL  47 

(2)  Polycyclohexane  derivative. 

(3)  An  aggregate  of  groups  of  variable  and  undetermined 
dimensions,  of  which  only  the  ultimate  terms  are  known, 
viz.,  CH2OH,  CHOH,  CO  ;  but  the  anhydride  forms  of  the 
alcoholic  OH  groups,  and  the  position  or  positions  of  the 
CO  groups  remain  undetermined. 

Constitutional  moisture  is  retained  by  the  cellulose  in  its 
air-dry  state,  varying  between  6  and  8  per  cent,  according 
to  temperature  and  saturation  of  surrounding -air. 

Solvents. — Cellulose  is  insoluble  in  all  neutral  solvent 
liquids.  Is  dissolved  by 

(1)  Concentrated  solutions  of  zinc  chloride  on  heating  at 
80°  to  100°. 

(2)  Solution  of    zinc  chloride  (1  part)  in  concentrated 
hydrochloric  acid  (2  parts)  in  the  cold. 

(3)  Solution     of     cupric    oxide    (hydrate)    in    aqueous 
ammonia  in   the   cold.     The   cellulose  may  be  recovered 
quantitatively  from  these  solutions,  though  constitutionally 
changed. 

Reactions. — The  above  reactions  resulting  in  solution  of 
the  cellulose  are  characteristic  ;  otherwise  it  is  exception- 
ally non-reactive.  By  dilute  solutions  of  iodine,  in  presence 
of  certain  dehydrating  agents,  it  is  coloured  blue. 

CELLULOSE  COMPOUNDS,  i.e.,  SYNTHETICAL  DEKIVATIVES. 
—ESTERS  (a)  NITRATES. — By  direct  reaction  with  nitric  acid, 
usually  in  presence  of  sulphuric  acid,  in  which  case  unstable 
mixed  esters  are  formed  as  a  stage  in  the  reaction,  the 
N03  displacing  the  S04H  residues.  The  esters  are  formed 
without  sensible  structural  modification.  They  are  purified 
from  residual  S04H  by  prolonged  boiling  with  water,  and 
are  then  "  stable."  A  series  of  these  esters  are  known,  the 


48  WOOD   PULP  AND  ITS  USES 

highest  approximating  to  the  trinitrate  (Ce)  (gun-cotton) 
the  intermediate  terms — dinitrate — being  soluble  in  ether- 
alcohol  (collodion  cotton),  the  lowest  having  physical  pro- 
perties but  little  different  from  the  original  cellulose. 

These  esters  are  variously  formulated  as  nitrates  of  a 
reactive  unit  of  CG — Ci2 — €24  dimensions. 

Solvents. — The  special  solvents  of  these  esters  are  acetone, 
ether-alcohol,  nitrobenzene. 

Saponification. — By  certain  alkaline  and  reducing  agents 
(alkaline  sulphydrates)  the  nitric  groups  are  eliminated  and 
cellulose  regenerated. 

(b)  ACETATES. — By  reaction  with  acetic  anhydride  under 
various  conditions :  (1)  at  110°  direct  formation  of  mono- 
acetate  (Ce)  insoluble  in  all  neutral  solvents  and  in  the 
solvents  of   cellulose.     (2)  At   140°  to  160°,  formation  of 
higher  acetates,  attended  by  solution  in  the  reaction  mix- 
ture.    (3)  In  presence  of  catalytic  agents  (ZnCU — H2S04 — 
H3P04)  at  intermediate  temperatures  ;  H2S04  determines 
reaction  at  25°  to  35°.     The  products  are  usually  mixtures 
of   tri-  and  tetracetate.     (4)  When  the  reaction  mixtures 
are  diluted  with  hydrocarbon  the  fibrous  cellulose  may  be 
acetylated  without  solution  or  sensible  structural  change. 

Solvents  of  the  higher  acetates,  chloroform,  acetone, 
phenol. 

Saponification. — The  acetyl  groups  may  be  removed  by 
boiling  with  alkaline  solutions,  the  cellulose  being  regene- 
rated. In  quantitative  determinations  the  saponification 
may  be  effected  by  digestion  with  normal  sodium  hydrate 
diluted  with  an  equal  volume  of  alcohol. 

(c)  ACID- SULPHURIC  ESTERS. — By  the  action  of  sulphuric 
acid  an  extended  series  of  esters  is  formed,  which  have  been 


CELLULOSE  AS  A  CHEMICAL  INDIVIDUAL  49 

described  as  cellulose  sulphuric  acids.  But  they  are 
certainly  derivatives  of  products  of  resolution.  The  first 
stage  results  in  the  formation  of  a  disulphuric  ester 
C6H803  (S04H)2,  but  its  relationship  to  the  parent  complex 
is  doubtful.  The  ester  is  soluble  in  water ;  the  Ca,  Ba,  and 
Pb  salts  are  insoluble  in  alcohol.  By  progressive  hydrolysis 
the  cellulose  is  ultimately  resolved  to  dextrose. 

(d)  ACETO- SULPHATES     AND    MIXED    ESTERS,   containing 
the  S04H  residues  associated  with  acetyl  and  other  negative 
groups  in  combination,  are  obtained  when  sulphuric  acid  is 
allowed  to  act  under  regulated  conditions  simultaneously 
with  other  esterifying    agents.     Thus  a  mixture  of  acetic 
anhydride    (50   parts),  glacial  acetic  acid  (50  parts),  and 
sulphuric  acid  (4  to  6  parts)  acts  rapidly  at  30°  to  40°.     The 
first  product  appears  to  be  a  neutral  body  of  the  empirical 

formula, 

(4  C6H70)S04(C2Hs02)10, 

and  under  the  action  of  water  to  undergo  an  internal 
hydrolysis,  the  S04  group  becoming  S04H,  which  forms  a 
stable  combination  with  bases.  The  Mg,  Ca,  Zn  salts  are 
insoluble  in  water,  but  soluble  in  acetone  (see  p.  237). 

(e)  BENZOATES  result  from  the  action  of  benzoyl  chloride 
in  presence  of  alkaline  hydrates.     A  monobenzoate  (C6)  is 
obtained  by  treating  cellulose  with  a  solution  of  sodium 
hydrate  of  10  per  cent.  (NaOH)  strength,  and  shaking  with 
benzoyl  chloride.     This  benzoate  is  formed  with  only  slight 
structural  change.     The  dibenzoate  (C6)  is  obtained  by  the 
interaction  of  benzoyl  chloride  and  alkali-cellulose  (mer- 
cerised cotton)  in  presence  of  sodium  hydrate  solution  (15 
per  cent.  NaOH).     Its  formation  is  attended  by  structural 
change  ;  the  fibrous  cellulose  is  disintegrated,  the  dibenzoate 

W.P.  E 


50  WOOD  PULP  AND  ITS  USES 

being  an  amorphous  substance.  The  dibenzoate  is  soluble 
in  acetic  acid,  chloroform. 

MIXED  ESTERS,  containing  the  benzoyl  and  nitric  residues, 
result  from  the  action  of  nitric  acid  upon  the  benzoates. 
Simultaneously  a  nitro-group  enters  the  benzoyl  residue. 

ALKALI  CELLULOSE. — The  fibrous  cellulose  undergoes  con- 
siderable structural  modification  under  the  action  of  solutions 
of  sodium  hydrate  of  12  to  25  per  cent.  NaOH.  There  is  a 
definite  synthetical  reaction  in  the  ratio  C6Hi005 :  2  NaOH, 
which  is  a  stage  in  the  formation  of  the  dibenzoate  (supra). 

The  compound  is  completely  dissociated  by  water :  by 
treatment  with  alcohol  an  equilibrium  is  reached  when  the 
reagents  are  associated  in  the  ratio  C^H^oOioNaOH. 

The  alkali -cellulose  hydrate,  of  composition 

Cellulose         .         .         30  \ 

Sodium  hydrate     .         15    Cellulose  :  Sodium  hydrate, 

Water    .         .         .         J    C'H"°*         2  NaOH 

is  the  first  stage  in  the  synthesis  of  cellulose  xanthogenic 
acid,  which  results  from  the  interaction  of  the  alkali  cellulose 
and  carbon  disulphide  at  ordinary  temperatures.  The 
sodium  salt  is  soluble  in  water.  It  is  an  unstable  compound, 
the  solution  undergoing  spontaneous  progressive  c-hange. 
The  solution,  which  is  highly  colloidal,  finally  solidifies. 
By  reason  of  the  characteristic  reaction  of  the  xanthates 
with  iodine, 

OX    XO  OX  -  XO 

CS  CS  +  I2  =  2NaI.  +  CS<  >CS, 

SNaNaS  S      -     S 

the  progress  of  the  change  may  be  followed,  the  essential 
feature  being  the  elimination  of  the  CS2  residues  with  re- 


CELLULOSE  AS  A  CHEMICAL  INDIVIDUAL  51 

aggregation  of  the  cellulose  units.  Well-marked  stages  in 
the  series  occur  at  the  points  denoted  by  the  empiri- 
cal formulae  C^HigOgCSSNa.  The  former  represents  an 
equilibrium  attained  after  the  solution  has  remained  for 
some  hours  at  the  ordinary  temperature :  the  latter  is  reached 
in  from  three  to  four  days.  The  cellulose  under  the  reaction 
acquires  a  more  acid  character,  an  additional  OH  group 
combining  with  alkali.  The  lower  terms  of  the  series, 
though  insoluble  in  water  or  dilute  saline  solutions,  are 
dissolved  by  the  addition  of  sodium  hydrate.  The  sodium 
atom  in  combination  with  the  CSS  residue  is  not  attacked 
by  weak  acids,  such  as  acetic  acid.  By  double  decomposition 
with  soluble  salts  of  Cu,  Zn,  etc.,  the  corresponding  xanthates 
are  produced  as  insoluble  colloidal  precipitates. 

In  the  above  reactions  the  cellulose  aggregate  is  main- 
tained ;  the  solutions  of  the  derivatives  are  viscous  and 
colloidal ;  but  the  following 

Reactions  of  decomposition,  which  are  determined  by 
hydrolytic  and  oxidising  agents,  the  directions  of  resolution 
are  extremely  various  and  the  relationships  of  the  products 
to  the  original  aggregate  are  undetermined. 

(a)  SULPHURIC   ACID,    sp.   gr.    T55 — 1'65,   dissolves   the 
cellulose  as  a  disulphuric  ester ;  but  decomposition  attends 
the  reaction,  and  on  diluting  and  boiling  the  hydrolysis  is 
carried  to  the  extreme  molecular  limit,  the  final  product 
being  dextrose. 

(b)  HYDROBROMIC  ACID  in  ethereal  solution  attacks  the 
cellulose  profoundly  with  production  of  brom-methyl  fur- 
fural.    The  formation  of  this  compound  indicates  a  previous 
or  intermediate  stage  in  which  the  products  of  resolution 
are  molecular  ketonic  bodies  of  carbohydrate  constitution. 


52  WOOD  PULP  AND  ITS  USES 

(c)  HYDROCHLORIC  ACID  in  presence  of  water,  dilute  sul- 
phuric acid,  and  acids  generally,  attacks  the  cellulose  aggre- 
gate with  production  of  a  variety  of  derivatives.     (1)  In- 
soluble :  These  are  generally  termed  hydrocelluloses.     They 
are  disintegrated  residues  of  the  original  fibres ;  they  differ 
chemically  from  the  parent  aggregate  in  the  presence  of 
free  aldehydic  groups,  and  in  readily  yielding  to  the  action 
of  alkalis.     (2)  Soluble  molecular  products,  chiefly  dextrine 
and  dextrose. 

(d)  ALKALINE  HYDRATES  and  ALKALIS  generally  have  little 
action  on  cellulose  in  the  form  of  dilute  solutions — even 
when  treated  at  elevated  temperatures.      Sodium  hydrate  in 
solution  of  concentrations  of  12  per  cent.  NaOH  and  upwards, 
combines  with  the  cellulose,  producing  profound  structural 
modifications    (mercerisation),   but   without   resolving   the 
aggregate. 

At  higher  concentration  and  temperature  the  cellulose  is 
partially  dissolved ;  but  even  under  the  conditions  of  a 
"  fusion  "  at  180°  the  resolution  is  limited  to  the  conversion 
into  alkali  soluble  modifications,  which  are  precipitated  in 
the  colloidal  form  on  diluting  and  acidifying.  At  higher 
temperatures  (250°)  and  with  larger  proportions  of  the 
alkaline  hydrates,  the  cellulose  is  resolved  into  acid  products 
of  low  molecular  weight,  chiefly  acetic  acid  and  oxalic  acid. 

Oxidants. — The  directions  of  oxidation  of  cellulose  are 
likewise  extremely  diversified.  The  aggregate  manifests 
considerable  resistance  to  alkaline  oxidants  in  dilute  form, 
e.g.,  solutions  of  the  hypochlorites,  permanganates  ;  but  when 
the  limit  is  passed  the  oxidations  which  result  are  drastic 
in  the  sense  that  the  soluble  products  are  of  low  molecular 
weight,  chiefly  carbonic  and  oxalic  acids.  The  insoluble 


CELLULOSE  AS  A   CHEMICAL  INDIVIDUAL  53 

fibrous  residues,  more  or  less  disintegrated,  are  known  as 
oxycelluloses.  They  contain  free  aldehydic  groups,  are 
easily  attacked  by  hydrolysing  agents,  and  on  boiling  with 
hydrochloric  acid  (1*06  sp.  gr.)  are  decomposed  with 
production  of  some  furfural. 

Resolved  by  the  action  of  concentrated  solutions  of  the 
kypocltlorites,  cellulose  yields  chloroform  and  carbon-tetra- 
chloride.  The  hypobromites  give  the  corresponding  bromine 
derivatives.  Nitric  acid  (1*25  sp.  gr.)  at  180°  converts 
cellulose  into  a  series  of  "  oxycelluloses,"  which  are  resolved 
on  boiling  with  calcium  hydrate  into  acid  products,  among 
which  isosaccharinic  and  dioxybutyric  acids  have  been 
identified.  In  the  original  oxidation  small  quantities  of  the 
higher  dibasic  acids — saccharic  and  tartaric  acids — are  pro- 
duced, but  the  main  products  are  oxalic  and  carbonic  acids. 

With  chromic  acid  an  endless  series  of  oxidations  may  be 
effected,  the  degree  of  action  depending  upon  the  proportion 
of  the  active  oxidant  and  the  associated  hydrolytic  action  of 
mineral  acids.  The  oxycelluloses  produced  are  distinguished 
by  relatively  large  yield  of  furfural  when  decomposed  by 
boiling  HC1  Aq  (1/06  sp.  gr.).  In  presence  of  sulphuric 
acid  there  ensues  complete  combustion,  and  the  reaction  is 
the  basis. of  quantitative  analytical  methods. 

Resolution  by  Ferment  Actions. — Under  the  actions  of 
specific  organisms  the  cellulose  complex  is  totally  resolved, 
the  main  products  being  methane,  hydrogen,  and  carbonic 
and  fatty  acids.  The  decomposition  may  be  associated  with 
the  action  of  an  enzyme ;  but  a  remarkable  feature  of  the 
process  is  the  absence  of  intermediate  products,  at  least  in 
the  cases  hitherto  investigated.  In  the  digestive  tract  of 
the  herbivora  cellulose  is  resolved,  and  from  the  investiga- 


54  WOOD  PULP  AND  ITS  USES 

tion  of  the  process,  necessarily  by  indirect  observations,  it 
appears  that,  in  addition  to  a  destructive  resolution  to 
ultimate  gaseous  products,  there  occurs  a  resolution  to 
proximate  groups  of  high  nutritive  value,  which  are 
assimilated  by  the  animal  organism. 

Resolution  by  Heat;  Destructive  Distillation. — The  decom- 
positions of  cellulose  at  temperatures  exceeding  250°  are 
necessarily  extremely  complex. 

The  groups  of  products  show  an  average  production  : 

Solid  Liquid  Gaseous 

30  per  cent.  50  per  cent.  20  per  cent. 

Charcoal  or  pseudo-  Containing  Chiefly 

carbon  Acetic  acid  (2  per  cent.)     CO  and  C02 

Methyl  spirit  (7  per  cent.) 
Acetone,  furfural 
tar  (12  per  cent.) 

the  actual  proportions  and  composition  of  these  mixtures 
varying  with  the  temperature  and  duration  of  the  heating. 
General  View  of  the  Decomposition  of  Cellulose. — It  is 
clear  that  the  cellulose  complex  breaks  down  under  destruc- 
tive influences,  in  directions  depending  upon  the  nature 
of  the  attacking  agent,  its  concentration,  and  all  the 
surrounding  physical  conditions.  The  study  of  these 
decompositions  has  thrown  but  little  light  on  the  actual 
nature  and  constitution  of  the  cellulose  aggregate ;  for  the 
reason,  perhaps,  that  we  have  endeavoured  to  maintain  a 
basis  of  interpretation  such  as  is  applicable  to  ordinary 
molecular  compounds  or  complexes.  If  we  regard  cellulose 
as  the  analogue  of  a  complex  salt  in  presence  of  water,  and 
endeavour  lo  follow  the  reactions  of  decomposition  as  we 


CELLULOSE  AS  A  CHEMICAL  INDIVIDUAL          55 

should  the  changing  equilibrium  of  a  colloidal  salt  solution 
under  the  action  of  reagents,  we  have  a  basis  of  working 
hypotheses  which  will  be  found  to  stand  the  general  test  of 
credibility — that  is,  they  tend  to  progress  in  investigation. 
We  make  this  observation  in  reference  to  the  matter  which 
we  have  just  endeavoured  to  reduce  to  short,  systematic 
expression,  but  which  obviously  cannot  effectually  be  so 
treated,  because  it  involves  the  entire  theoretical  basis  of 
our  subject — that  is,  the  actual  state  of  matter  and  the 
distribution  of  the  reactive  unit-groups  in  the  cellulose 
complex ;  and  this  basis  is  as  yet  entirely  undetermined. 

The  Cellulose  Group. — From  the  typical  cellulose  we  pass 
to  the  diversified  group  of  celluloses.  Their  general  charac- 
teristics are  those  of  the  prototype ;  the  variations  they 
present  are  especially  such  as  involve  the  undetermined 
factors  of  constitution.  With  these  there  are  certain  cor- 
relative variations  which  afford  an  empirical  basis  of 
classification.  These  are  (a)  the  degree  of  resistance  to 
hydrolytic  and  to  oxidising  agents,  (b)  the  percentage 
yield  of  furfural  when  decomposed  by  boiling  HC1  Aq, 
(c)  elementary  composition,  in  respect  of  the  ratio  C  :  0. 

The  fibrous  celluloses  are  grouped  as  follows: — 

Cotton  Wood  cellulose     Cereal  cellulose 

sub-group  A      sub-group  B         sub-group  C 
Type.  Bleached  cotton.  Jute  cellulose.     Straw  cellulose. 

Elementary    j  (C)  44'0—  44'4  43'0— 43'5       41'5— 42'5 
Composition    (  (0)       50*0  51'0                  53'0 
Furfural     .         .      01— 0'4  3'0— 6'0         12'0— 15*0 
Other  character- 
istics      .        .     No  active  Some  free  Considerable 
CO  groups.  CO  groups.      reactivity  of 

CO  groups. 


56  WOOD  PULP  AND   ITS  USES 

Of  these  groups  the  following  points  may  be  noted  :— 

A. — Comprises,  in  addition  to  cotton,  other  industrially 
important  celluloses,  e.g.,  flax,  hemp,  and  rhea.  They 
occur  in  the  plant  world  in  association  with  compounds 
easily  removed  by  the  action  of  alkalis.  They  pass  through 
the  cycle  of  reactions  involved  in  their  solution  as  xanthate, 
without  hydrolysis  to  soluble  derivatives. 

B. — These  celluloses  are  obtained  as  products  of  decom- 
position of  a  compound  cellulose.  They  may  be  regarded 
as  partially  hydrated  or  hydrolysed.  They  are  more 
readily  attacked  by  hydrolysing  agents  and,  in  the  xanthate 
reactions,  are  partially  resolved  to  alkali-soluble  derivatives. 

C. — These  celluloses  are  in  most  cases  a  complex  of 
structural  elements,  and  not  homogeneous  chemically. 
They  are  still  less  resistant  than  the  preceding  group,  and 
more  especially  the  furfural-yielding  components,  which  are 
selectively  attacked  under  certain  conditions. 

The  cellulose  groups,  as  above,  pass  by  imperceptible 
gradations  into  a  heterogeneous  class  of  natural  products 
which,  while  possessing  some  of  the  characteristics  of  the 
celluloses  proper,  are  so  readily  resolved  by  hydrolytic  treat- 
ment that  they  must  represent  a  very  different  constitutional 
type  or  types.  To  this  group  of  complex  carbohydrates  the 
class-name  hemicellulose  has  been  assigned.  They  are  struc- 
turally different  from  the  fibrous  celluloses,  occurring  mostly 
in  the  cellular  form  (parenchyma,  etc.).  They  differ  in  physio- 
logical function  and  in  being  readily  resolved  by  hydrolysis 
into  the  crystalline  monoses. 

II. 

We  have  now  to  deal  with  the  complex  of  groups  in  com- 
bination with  the  cellulose  in  the  ligno-celluloses.  They 


CELLULOSE  AS  A  CHEMICAL  INDIVIDUAL  57 

are  conveniently  grouped  under  the  neutral  term  "  non- 
cellulose  " ;  but  in  view  of  their  leading  characteristics, 
which  are  those  of  the  di-ketones,  or  more  particularly 
quinones,  they  are  more  aptly  described  by  the  term 
"  lignone." 

A  ligno-cellulose  as  a  compound  of  cellulose  and  lignone 
is  differentiated  from  cellulose  in  many  important  respects. 
First,  in  elementary  composition  it  presents  a  striking 
contrast,  as  will  be  seen  from  the  subjoined  numbers  :— 

Cellulose.  Typical  Ligno-celluloses. 

Jute.          Pine  wood.    Beech  wood. 

Carbon    .         .         44*4  47*0  48'4  491 

Hydrogen         .  61  61  6'3  6'2 

Oxygen    .         .         49*5  46'9  45*3  44'7 

Applying  a  statistical  calculation  to  one  of  the  ligno-cellu- 
loses,  we  may  conclude  that  the  lignone  complex  is  a  body 
of  much  higher  carbon  contents  (57  per  cent.)  than  cellulose 
(44  per  cent.).  Thus  : — 

Carbon. 

Cellulose    75  *  44  83'00 

Ligno-cellulose  100 

Jute  25  X  57  14'25 

Lignone       -^- 

47'25 

Further  we  may  calculate  from  the  figures  that  the  ratio  of 
the  elements  in  the  lignone  is  approximately  CG  :  He :  Oa 
expressed  on  a  C6  unit. 

Two  reactions  of  the  lignone  are  of  importance  in  enabling 
us  to  fix  this  empirical  formula  more  closely,  as  well  as 
certain  constitutional  relationships. 


58  WOOD  PULP  AND  ITS   USES 

Chlorine. — The  lignone  reacts  quantitatively  with  chlor- 
ine, combining  with  the  halogen,  that  is,  in  a  characteristic 
and  invariable  proportion.  In  the  case  of  jute  this  propor- 
tion is  8  per  cent,  of  the  ligno-cellulose,  and  an  equal 
proportion  is  converted  with  hydrochloric  acid.  In  the 
woods,  the  chlorine  combining  is  higher  in  proportion 
to  the  higher  percentage  of  lignone  groups ;  but  the 
hydrochloric  acid  produced  is  much  higher.  The  chlor- 
inated complex  is  soluble  in  certain  neutral  solvents,  such 
as  alcohol.  The  analysis  of  the  chlorinated  derivative 
obtained  from  jute  establishes  the  formula  CigHigC^Og,  and 
the  investigation  of  the  reaction  has  shown  that  the  lignone 
is  integrally  attacked.  The  chlorinated  derivative  reacts 
with  sodium  sulphite  in  aqueous  solution,  and  is  converted 
into  a  soluble  sulphonated  derivative,  being  quantitatively 
eliminated  from  the  cellulose.  This  reaction  is  employed 
for  the  quantitative  resolution  of  the  ligno-cellulose  and  the 
estimation  of  its  cellulose  contents.  The  chlorinated  group 
in  the  lignone  derivative  is  identified  as  a  quinone  chloride, 
and  the  complex  thereby  definitely  connected  with  the 
aromatic  or  benzene  group  of  carbon  compounds.  The 
chlorinated  group  is  converted  by  treatment  with  nascent 
hydrogen  (zinc  and  sulphuric  acid)  into  a  derivative  of 
pyrogallol ;  and  the  complex  is  thus  closely  related  to 
the  "tannins,"  of  which  the  trihydroxybenzenes  are  as 
characteristic  constituent  groups.  Incidentally  it  has  been 
shown  that  the  lignone  complex,  in  further  contrast  to 
cellulose,  contains  but  a  small  proportion  of  free  hydroxy 
groups. 

Bisulphites. — The  lignone  reacts  integrally  and  selectively 
with  the  bisulphites  of  the  alkali  and  alkaline  earth  metals  ; 


CELLULOSE  AS  A  CHEMICAL  INDIVIDUAL  ,59 

a  ligno-cellulose  treated  with  solutions  of  these  compounds 
at  elevated  temperatures  and  under  pressure  is  quantita- 
tively resolved  into  cellulose  obtained  as  an  insoluble  residue 
of  the  ultimate  fibres,  and  soluble  sulphonated  derivatives 
of  the  lignone.  This  process  is  not  only  quantitative,  but 
fulfils  the  further  requirements  of  an  economical  industrial 
process,  and  it  is  therefore  extensively  employed  in  the 
preparation  of  wood  cellulose  or  wood  pulp  from  the  woods 
of  the  conifers.  As  an  industrial  process  it  will  be  fully 
described  in  a  subsequent  chapter.  At  this  point  we  are 
concerned  with  the  nature  and  composition  of  the  soluble 
by-products,  which  are,  in  effect,  the  lignones  in  combina- 
tion with  the  bisulphite  residues.  These  compounds  have 
been  separated  in  various  derivative  forms  and  analysed,  and 
the  following  empirical  formulae  have  been  established  :— 
(Cellulose,  pp.  200,  201). 

From  analyses  of  product  precipitated  by  hydrochloric 
acid 


From  analyses  of  compounds  obtained  by  precipitation  with 
lead  oxide 


Brominated  derivative 


The  parent  molecule  or  lignone  complex  of  the  wood  may 
be  taken  to  have  the  composition 

C24H24  (CHa)  20lQ. 

The  above  reactions  of  the  lignone  complex  are  specially 
characteristic  ;  they  are  simple  and  quantitative,  and  as 
they  are  devoid  of  secondary  complications,  the  derivatives 
are  in  simple  relationship  to  the  parent  complex.  But  the 


60  WOOD  PULP  AND  ITS  USES 

more  complete  characterisation  of  the  lignone  is  necessarily 
based  upon  the  study  of  reactions  of  decomposition. 

These  are,  however,  extraordinarily  complex,  and  in 
accordance  with  our  present  treatment  of  the  subject,  our 
description  will  be  limited  to  a  general  outline. 

Chromic  Acid  in  presence  of  a  hydrolysing  acid  attacks 
the  lignone  complex  in  the  cold.  The  reaction  has  been 
specially  studied  in  the  case  of  jute.  The  important 
features  of  the  decomposition  is  the  complete  breakdown  to 
acid  products  of  the  lowest  molecular  weight — carbonic, 
formic,  acetic  and  oxalic  acids.  This  bears  a  direct 
interpretation  in  reference  to  the  constitution  of  lignone  ; 
it  excludes  hydrocarbon  nuclei  of  any  but  the  smallest 
dimensions,  notwithstanding  the  large  dimensions  of  the 
lignone  formula ;  and  further  implies  a  relatively  high 
proportion  of  CO  groups,  alternating  in  periods  of  short 
dimensions  with  hydrocarbon  groups.  When  the  reaction 
is  applied  to  the  ligno-cellulose  the  action  is  confined  to 
the  lignone,  so  far  as  it  may  be  described  as  a  destructive 
oxidation,  but  extends  to  the  cellulose  in  converting  it  into 
an  "  oxycellulose  "  largely  soluble  in  alkaline  solutions. 

Nitric  Acid  attacks  the  ligno-celluloses  at  all  concentra- 
tions and  temperatures,  and  undermost  conditions  effects  a 
destructive  resolution  of  the  lignone.  The  following  are 
the  results  of  a  statistical  investigation  of  the  decomposition 
of  jute  ligno-cellulose  :— 

Ligno-cellulose  and  Nitric  Acid  (10%  HNO3)  at  60—80°. 

Cellulose  a.     Oxalic  acid.     Complex  unstable  acid. 
Solid  products         .     63—56%         40—55% 

Volatile  products   .  Acetic  and  Formic  acids  (14 — 18%) 

Gaseous  products  .     From  HNO3  From  Ligno-cellulose 

N2O4,N2O2,N2O,N2,HCN       CO2— CO— HCN 


CELLULOSE  AS  A   CHEMICAL  INDIVIDUAL  61 

Cellulose  a  is  a  more  stable  and  resistant  cellulose 
by  contrast  with  cellulose  /3  which  is  attacked  under 
the  above  conditions,  though  resistant  to  chlorine,  and 
therefore  to  the  conditions  of  the  process  described  on 
p.  59. 

This  reaction  has  been  the  subject  of  various  patents  and 
attempts  to  develop  upon  it  an  industrial  process  for  the 
preparation  of  cellulose. 

As  regards  the  theoretical  bearings  of  these  results,  the 
far-reaching  resolution  of  the  lignone  under  an  attack 
which  cannot  be  described  otherwise  than  as  of  very 
moderate  intensity,  further  confirms  the  conclusions  as  to 
the  prevalence  of  CO  groups  in  the  lignone  complex, 
alternating  with  hydrocarbon  groups  of  relatively  small 
dimensions.  Of  other  acid  resolutions  we  shall  mention  as 
yielding  characteristic  products : 

Hydrochloric  Acid. — The  aqueous  acid  at  a  concentration 
of  12  per  cent.  HC1  (sp.  gr.  1*06)  determines  a  highly 
complex  series  of  changes  at  the  boiling  point.  Both  the 
cellulose  and  lignone  are  profoundly  attacked.  The 
characteristic  product  is  the  volatile  aldehydic  substance 
furfural,  which  distils,  and  may  be  quantitatively  estimated 
in  the  distillate.  The  yields  of  this  aldehyde  are  charac- 
teristic of  the  various  types  of  ligno-celluloses  : — 

Average  yields  of  furfural  f  Jute       ....         8'0 

from   typical    ligno-  j  Beechwood     .         .         .       18*0 

celluloses.  „         purif.   Alkalis       12'0 

Coniferous  woods     .     4*0 — 5*0. 

It  may  be  noted  that  the  furfural-yielding  constituents 


62  WOOD  PULP  AND  ITS  USES 

of  the  ligno-cellulose  occupy  an  intermediate  position  in 
function  and  relation  between  the  lignone  and  cellulose. 
Thus  in  isolating  the  cellulose  by  the  chlorination  process, 
a  cellulose  is  obtained  which  yields  6 — 8  per  cent,  furfural 
on  boiling  with  the  acid  ;  this  cellulose  is  the  /3  cellulose 
mentioned  on  p.  61.  Further,  on  treating  the  ligno- 
celluloses  with  alkaline  hydrates  in  the  cold,  a  constituent 
is  dissolved,  which  is  separated  on  acidifying  the  solution, 
as  an  amorphous  colloidal  precipitate.  Beechwood  yields 
this  product  in  exceptional  proportion.  It  is  known  as 
wood  gum.  It  is  characterised  by  its  high  yield  of  furfural, 
viz.,  33 — 48  per  cent,  according  to  its  degree  of  "purity," 
i.e.,  the  freedom  from  associated  groups  of  the  characteristic 
component.  This  body  is  a  "  Pentosan,"  an  anhydride 
of  the  C5  sugars,  an  analogue  of  starch,  which  may  be 
regarded  as  an  anhydride  of  the  CG  sugar  dextrose.  These 
C5  sugars  do  not  occur  free  in  the  plant  world  ;  but  in  the 
form  of  these  amorphous  and  colloidal  anhydrides  are  very 
widely  distributed  as  constituents  of  plant  tissues.  The 
condensation  to  furfural  as  a  main  reaction,  though 
characteristic  of  these  C5  sugars,  is  not  an  exclusive 
constitutional  index,  and  there  are  many  possible  group- 
ings which  might  undergo  this  condensation.  It  is  there- 
fore usual  to  adopt  the  more  general  term  of  furfuroid 
in  describing  such  plant  or  constituents  as  yield  furfural ; 
the  narrower  identification  as  a  pentosan  depends  upon 
the  actual  production  of  the  C5  sugars  as  products  of 
hydrolysis. 

Alkaline  Decompositions. — The  lignone  group  is  attacked 
by  alkaline  solutions  at  elevated  temperatures  and  converted 
into  soluble  derivatives,  which  are  acid  in  character,  but 


CELLULOSE   AS  A  CHEMICAL  INDIVIDUAL  63 

for  the  most  part  of  ill-defined  constitution.  The  cellulose, 
resisting  the  action  of  these  reagents,  is  separated  and  is 
obtained  as  a  disintegrated  mass  of  fibrous  or  cellular 
units,  constituting  a  "  pulp."  Upon  these  decompositions 
are  based  an  important  group  of  industrial  processes  for 
the  preparation  of  wood  pulps,  which  will  be  found 
described. 

Having  by  this  discussion  obtained  a  general  knowledge 
of  the  ligno-celluloses  as  chemical  compounds,  and  also  of 
the  ultimate  component  groups  of  both  lignone  and  cellulose, 
we  are  in  a  better  position  to  deal  with  certain  special 
properties  and  reactions  of  the  ligno-celluloses,  either 
involved  in  the  industrial  applications  of  those  products 
which  they  to  some  extent  define  and  limit,  or  employed  in 
their  quantitative  estimation  when  present  as  constituents 
of  a  fibrous  mixture. 

Some  of  the  characteristic  reactions  of  the  ligno-celluloses, 
about  to  be  described,  appear  to  be  due  to  actual  furfural 
derivatives  present  in  the  complex.  The  pentosans,  on  the 
other  hand,  if  assumed  to  be  the  mother  substance  of  the 
furfural  obtained,  are  saturated  derivatives,  and  their 
composition  and  properties  are  such  as  would  leave  many 
of  the  characteristics  of  the  lignone  complex  unaccounted 
for. 

Hydriodic  Acid  decomposes  the  ligno-celluloses  with 
liberation  of  methyl  iodide,  and  the  production  and  estima- 
tion of  this  volatile  product,  is  taken  as  the  index  and 
quantitative  measure  of  methoxyl  OCH3  groups  present  in 
the  ligno-cellulose.  This  ethereal  group  is  a  further 
"  chemical  constant  of  lignification."  The  percentages  of 
ethereal  methyl  groups  are  remarkably  uniform  for  a  very 


64 


WOOD  PULP  AND  ITS  USES 


large  range  of  woods  or  ligno-celluloses.     The   following 
have  been  determined  (Cellulose,  p.  189) : — 

A.    WOODS. 

Stem 


Maple 


Acacia 

Birch 
Pear   . 
Oak     . 

Alder  . 
Ash 


Fir 


Pine 


Cherry 
Larch 

» 

Lime  . 
Mahogany 
Walnut 

» 

Poplar 
Beech 


,,     extracted1 
,,     shavings  . 

Branch     . 

Extracted 

3  years  old 

Stem 


Stem          .... 
Shavings  from  stem . 
Stem  shavings  extracted  . 
Shavings  from  branches  . 
(Shavings    from    branches) 


CH8  p.ct. 

Acer  Pseudo-platanus,  L.  .  3'06 
.  3-05 
.  3-06 

Robinia  Pseud- Acacia,  L.    2-37 


Betula  alba 

Pyrus  communis,  L.  . 

Quercus  pedunculatus 

Alnus  glutinosa 
Fraxinus  excelsior,  L. 


(     extracted 
Stem 


Abies  excelsa 


(central  zone) 
(sap  wood) 


Stem 


Shavings  from  stem 
Stem 


shavings  . 


Abies  pectinata,  DC. 
Pinus  sylvestris,  L.    . 
Pinus  laricis 

Prunus  Avium,  L.     . 
Larix  eiiropcea,  DC.  . 

i»  »> 

Tilia  parvifolia 
Swietenia  Mahagoni,  L. 
Juglans  regia,  L. 

Populus  alba 
Fagus  sylratica 


2-57 
3-21 
2.86 
2-63 
•2-89 
2-71 
2-69 
2-66 
3-02 

2-91 

2-15 
2-25 
2-39 
2-59 
2-32 
2-45 
2-25 
2-05 
2-12 
2-38 
1-99 
2-68 
2-56 
2-66 
2-27 
2-69 
2-59 
3-02 
2-62 
2-70 


1  "  Extracted "  signifies  previously  exhausted  with  water,  alcohol, 
and  ether.  Otherwise  the  specimens  were  analysed  without  previous, 
preparation. 


CELLULOSE  AS  A  CHEMICAL  INDIVIDUAL          65 

CH3  p.ct. 

Elm    .        .    Stem          ....     Ulmus  campestris      .        .    2-92 
,,       .        .        ,,     shavings  extracted  ,,  ,,  .  2'75 

Willow       .  .        .        .        .        .     Salix  alba          .        .        .    2-31 

B.     FIBROUS  PRODUCTS. — Natural  and  prepared. 

Jute  (Lignocellulose) 1-87 

Swedish  filter  paper 0-0 

Cotton  0-0 

Flax,  unbleached  .         .         .         .         .       Linum  usitatissimum        .  O'O 

Hemp  ,, Cannabis  sativa         .         .  O29 

China  Grass,  unbleached       .         .         .       Bohmeria  nivea          .        .  O07 

Sulphite  (Cellulose')       ....       Pinus  sylvestris         .         .  0'34 

C.    MISCELLANEOUS. 

Cork Quercus  suber    .        .        .2-40 

.......  „  „       .        .         .     2-47 

Nutshells Juglans  regia     .        .        .     3*74 

Lignite  (Wolfsberg) 2-44 

Brown  coal 0-27 

In  reference  to  actual  molecular  proportions  it  is  to  be 
noted  that  in  the  sulphonated  derivatives  obtained  from 
the  lignones  of  coniferous  woods  the  proportion  is  indicated 
by  the  formula  C24H24(CH3)2SOi2.  The  localisations  of 
these  methyl  groups  is  a  present  object  of  investigations ; 
and  their  presence  is  established  in  the  celluloses  isolated 
from  the  ligno-celluloses.  This  is  taken  as  an  indication  of 
a  genetic  relationship  between  cellulose  and  lignone. 

We  may  now  set  out  the  main  features  of  the  chemistry 
of  the  ligno-celluloses  in  a  brief  resume  as  follows  :— 

With  the  typical  characteristics  of  the  celluloses  as 
complex  aggregates,  the  ligno-celluloses  similarly  react 
with  the  zinc  chloride  reagents  to  form  colloidal  solutions ; 
also  to  form  esters  with  nitric  acid,  acetic  anhydride 
and  benzoyl  chloride,  respectively  nitrates,  acetates,  and 

W.P.  F 


66  WOOD   PULP  AND  ITS  USES 

benzoates.  But  such  reactions  are  in  the  main  those  of 
the  cellulose  constituents  of  the  complex,  the  latter  remain- 
ing unresolved.  The  lignone  groups  with  which  the 
cellulose  is  combined  or  associated  are  sharply  differen- 
tiated from  the  cellulose  not  only  by  higher  carbon  per- 
centage and  low  molecular  proportion  of  OH  groups,  but 
by  constitution ;  they  are  unsaturated,  cyclic  compounds, 
and  hence  react  synthetically  with  chlorine,  bisulphites 
and  nitric  oxides. 

They  are  greedy  of  oxygen,  and  are  profoundly  attacked  by 
all  oxidising  agents,  are  even  subject  to  progressive  attack 
by  atmospheric  oxygen.  Hence  the  ligno-celluloses  as  con- 
stituents of  papers  lower  the  qualities  of  these  important 
industrial  products,  not  only  from  their  inferior  intrinsic 
paper-making  quality,  but  from  the  changes  which  take 
place  as  a  result  of  atmospheric  oxidation  :  these  are, 
discoloration  and  loss  of  tenacity.  Cellulose,  as  a  satu- 
rated compound,  is  free  from  this  cardinal  defect,  and  we 
have  practical  evidence  of  this  in  the  extraordinary 
resistance  to  atmospheric  influences  of  papers  and  textiles 
which  have  been  preserved  to  us  from  the  Middle  and 
earlier  ages. 

Associated  with  these  constitutional  features  we  have  a 
well  marked  and  diversified  dyeing  capacity  :  the  ligno- 
celluloses  are  dyed  easily  and  by  colouring  matters  of 
widely  varying  constitution,  whereas  the  celluloses  proper 
have  a  selective  or  limited  tinctorial  capacity. 

As  regards  intrinsic  "  colour,"  the  ligno-celluloses  occur 
in  forms  which  would  be  described  as  grey,  yellow  or  brown 
-—but  such  colours  are  mostly  due  to  associated  by-products. 

When  freed  from  these  by  certain  standard  methods  of 


CELLULOSE  AS  A  CHEMICAL  INDIVIDUAL          67 

"  bleaching "  they  assume  a  bright  cream  to  whitish 
colour.  But  bleaching  processes  are  based  upon  alkaline 
and  oxidising  treatments,  to  both  of  which  the  lignone  con- 
stituents are  extremely  sensitive.  Hence  the  limitations  of 
ligno-cellulose  textiles,  such  as  jute,  in  respect  of  colour. 
The  substance  will  not  sufficiently  resist  the  necessary  treat- 
ments for  a  "high  bleach."  Another  feature  of  inferiority 
is  a  joint  product  of  the  relative  shortness  of  the  ultimate 
fibre  and  want  of  resistance  to  the  chemical  actions  of 
hydrolysis  and  oxidation.  From  a  practical  point  of  view 
the  ligno-celluloses  are  composed  of  cellulose  units  of  short 
dimensions  (1 — 3  mm.)  cemented  together  by  the  lignone 
components.  When  these  are  removed  the  fibre  is  disin- 
tegrated ;  for  it  is  evident  that  structural  units  of  J  in.  length 
cannot  cohere,  and  the  strength  of  a  yarn  or  fabric  pre- 
senting this  condition  can  only  be  that  due  to  the  adhesion 
of  the  fibres,  as  in  a  sheet  of  paper.  When  wetted  the 
adhesion  is  reduced  to  a  fractional  proportion.  Hence  the 
bleaching  of  ligno-celluloses  is  a  matter  of  practical  com- 
promise, and  a  ligno-cellulose  fabric,  bleached  or  unbleached, 
is  always  tending,  however  slowly,  to  disintegration,  as 
a  result  of  the  attack  of  the  natural  and  all-pervading 
agencies  oxygen  and  water. 

It  is  necessary  for  a  thorough  grasp  of  the  chemical 
technology  of  the  woods,  to  take  the  logical  road  of 
studying  the  jute  fibre  as  a  structural  type,  and  the  jute 
fibre-substance  as  a  typical  ligno-cellulose.  From  the 
latter  point  of  view  it  occupies  the  mean  position  between 
the  celluloses  and  the  perennial  woods,  and  it  will  be 
found  to  be  generally  true  of  the  characteristic  reactions 
of  these  substances.  Thus  jute  is  attacked  by  the 

F  2 


68  WOOD   PULP  AND  ITS  USES 

cuprammonium  reagent  and  for  the  most  part  dissolved ; 
but  the  ligno-celluloses  of  the  woods  are  scarcely  affected. 
Strong  solutions  of  the  caustic  alkalis  produce  the  effects 
of  "  mercerisation  "  upon  jute  and  fibrous  ligno-celluloses  of 
similar  composition,  but  not  upon  the  woods.  Moreover, 
if  mercerised  jute,  retaining  the  soda  (NaOH)  be  exposed 
to  carbon  bisulphide,  synthesis  of  a  xanthogenic  acid 
occurs,  as  with  the  celluloses.  But  the  reaction  is  compli- 
cated by  the  presence  of  the  lignone  groups,  and  the 
product,  instead  of  being  entirely  soluble  to  a  structureless 
solution,  is  swollen  or  distended  by  water  to  practically 
indefinite  limits,  and  after  being  so  distended,  if  then 
decomposed  it  reverts  to  a  fibrous  mass.  In  the  case  of 
the  woods,  on  the  other  hand,  there  is  no  perceptible 
attack  even  on  prolonged  joint  action  of  the  alkali  and 
carbon  bisulphide.  The  higher  proportion  of  lignone  con- 
stituents in  the  woods,  with  decreased  percentage  of 
cellulose,  has  the  effect,  therefore,  of  producing  a  condition 
of  resistance  to  reaction,  or  chemical  inertness.  Doubtless 
this  is  related  to  the  physiological  functions  of  the  woods 
and  their  persistence  during  the  prolonged  period  of  life 
of  trees ;  and  this  property  of  inertness  is  attained  by 
increase  in  groups  which  are  highly  reactive  and  extra- 
ordinarily "  labile."  The  result  appears  to  be  paradoxical, 
and  involves  a  natural  equilibrium  of  obviously  profound 
significance. 

This  will  be  more  fully  appreciated  from  a  consideration 
of  certain  characteristic  colour  reactions  of  the  ligno- 
celluloses,  which  are  a  certain  measure  of,  being  quantita- 
tively related  to,  their  lignone  constituents. 

Ferric  Ferricyanide. —  The   red   solution   which   results 


CELLULOSE  AS  A  CHEMICAL  INDIVIDUAL  69 

from  the  interaction  of  ferric  salts  and  alkaline  ferri- 
cyanides  in  solution  thus  :— 

FeCla  +  K3FeCy6  =  3  KC1  +  Fe2Cy6 

colours  the  ligno-celluloses  a  deep  blue  as  a  result  of 
deoxidation  of  the  ferric  compound  and  reduction  to  the 
complex  cyanides  known  as  Prussian  blue,  Turnbull's 
blue,  etc.  These  separating  as  colloidal  hydrates  are 
deposited  in  a  state  of  intimate  union  with  the  ligno- 
cellulose  substance,  and  in  the  case  of  the  jute  fibre  it  is 
easy  to  see  by  microscopic  examination  that  the  colloidal 
blue  pigment  is  structurally  incorporated  with  the  fibre 
substance.  The  amount  so  combining  may  be  30 — 40  per 
cent,  of  its  weight,  without  changing  the  external  character- 
istics of  the  fibre,  i.e.,  form  and  lustre.  The  reaction  is  of 
use  in  following  the  progressive  elimination  of  the  lignone 
constituents  in  the  processes  of  isolating  cellulose. 

Students  who  wish  to  follow  up  this  interesting  reaction 
are  referred  to  Journ.  Soc.  Chem.  Ind. 

Phenols.  —  The  aldehydic  and  ketonic  constitution  of 
the  ligno-celluloses  determines  characteristic  reactions  with 
aromatic  hydroxy  derivatives  or  phenols.  One  of  these  is 
exceptionally  striking. 

Phloroglucol,  the  symmetrical  trihydroxybenzene  (CeH3  . 
01H  .  03H  .  05H)  in  solution  in  aqueous  hydrochloric  acid  of 
1*06  sp.  gr.  reacts  with  production  of  coloured  derivatives  of 
magenta-red  hue. 

The  depth  of  colour  developed  is  constant  for  any  given 
ligno-cellulose,  and  may  be  used  as  a  quantitative  estimation 
of  ligno-celluloses  in  intimate  admixture  with  non-reactive 
substances  such  as  cellulose. 


70  WOOD  PULP  AND  ITS  USES 

Ordinary  printing  papers  are  a  mixture  of  "  ground 
wood  "  pulp,  and  "  chemical  "  pulp  or  cellulose,  and  the 
depth  of  coloration  obtained  in  moistening  with  the 
"  phloroglucol  reagent  "  affords  an  approximate  measure  of 
the  proportion  of  the  former  or  ligno-cellulose. 

A  closer  study  of  the  reaction  has  shown  that  it  consists 
of  two  phases ;  the  coloured  bodies  result  from  a  minor 
reaction  reaching  a  maximum  with  less  than  1  per  cent, 
of  the  phenol  per  100  parts  of  the  ligno-cellulose :  the 
major  reaction  takes  place  without  development  of  colour 
and  "  fixes  "  a  further  6 — 7  per  cent,  of  the  phenol  in  com- 
bination as  a  product  of  condensation.  The  colour-reactions 
appear  to  be  due  to  aldehydes  of  the  furfural  type,  probably 
hydroxy  furfurals. 

As  a  result  of  this  further  investigation  a  more  strictly 
quantitative  method  has  been  devised  which  measures  the 
total  phenol  combining,  and  by  calculation  the  proportion  of 
ligno-cellulose  in  mixtures.  (See  Ber.  Deuts.  Chem.  Gcs., 
40,  3119,  1907.) 

Aromatic  Bases,  such  as  aniline  and  substituted  anilines 
react  with  constituent  groups  of  the  ligno-cellulose  complex, 
giving  characteristic  yellow  to  orange  colorations. 

With  dimethylparaphenylenediamine  the  reaction  is 
more  striking,  the  colour  developed  being  a  "  magenta  " 
red.  With  the  ligno-celluloses  in  their  normal  state  the 
colorations  are  constant,  and  are  therefore  an  approximate 
quantitative  measure  of  the  proportion  of  ligno-cellulose  in 
admixture  with  non-reacting  substances  such  as  cellulose. 
The  method  devised  by  Wurster  consists  in  developing  the 
colour  reaction  and  comparing  the  depth  of  colour  with  a 
graduated  scale  of  fixed  tints. 


CELLULOSE  AS  A  CHEMICAL  INDIVIDUAL          71 

It  is  to  be  noted  again  that  these  reactions  are  not 
characteristic  of  the  ligno-cellulose  as  such.  They  are 
weakened  by  treatment  of  the  ligno-celluloses  with  reagents 
of  feeble  intensity,  such  as  sulphurous  acid  and  sulphites 
under  conditions  which  leave  the  ligno-cellulose  itself 
unaffected.  They  are  reactions,  as  in  the  case  of  the 
phenols,  with  by  -  product  groups,  invariably  present. 
There  is  evidence  that  these  groups  are  the  same  as  those 
which  react  with  the  phenols.  (See  also  Ber.  Deuts.  Chem. 
Get.,  40,  3119.) 

Ligno-cellulose  and  Photo -chemical  Phenomena. 

We  cannot  close  this  theoretical  account  of  the  ligno- 
celluloses  without  introducing  the  researches  of  the  late 
W.  J.  Eussell  on  "  The  Action  of  Wood  on  Photographic 
Plates  in  the  Dark  "  (Phil.  Trans.  B.,  197,  281, 1904  ;  also 
Proc.  R.  S.  B.,  78,  385  ;  80,  376). 

We  are  indebted  to  Mr.  W.  F.  Bloch,  who  assisted 
Dr.  Kussell  in  these  investigations,  for  the  following  notes 
of  their  results  : — 

Russell  found  that  all  the  woods  were  able  to  give  definite 
pictures  upon  a  photographic  plate,  in  absence  of  light. 

The  action  takes  place  when  the  wood  is  kept  at  a 
considerable  distance  from  the  plate ;  but  for  perfect 
definition,  contact  was  necessary.  The  pictures  usually 
corresponded  with  the  visible  structure  of  the  wood ;  but  in 
some  cases  there  was  a  marked  differentiation. 

This  selective  activity  appeared  to  depend  in  part  upon  the 
resinous  constituents  of  the  wood  and  its  disposition  on  the 
cells ;  but  also  in  part  upon  the  nature  of  the  cell-wall 


72  WOOD  PULP  AND  ITS  USES 

structure  itself,  which  in  cases  offered  much  resistance  to 
the  passage  of  the  active  bodies. 

On  the  evidence  the  active  bodies  must  be  regarded  as 
an  emanation,  but  differing  entirely  from  radio-active 
emanations. 

All  the  properties  ascertained  identify  the  substance  with 
hydrogen  peroxide. 

Ordinary  photographic  dry-plates  may  be  used  to  produce 
this  effect ;  care  must  be  taken  to  select  such  as  have  been 
preserved  in  wrapping  materials  themselves  unable  to  act 
upon  the  plates. 

The  action  takes  place  slowly  at  ordinary  temperatures 
(one  day  to  twenty-one  days)  according  to  the  nature  of  the 
specimen,  but  rapidly  at  50 — 55°  C.  (half  to  eighteen 
hours). 

The  shorter  exposures  give  sharper  pictures,  which 
observation  accords  with  the  conclusion  that  the  active 
body  is  of  the  nature  of  a  vapour  or  volatile  compound. 

Bark  and  pith  structure  are  almost  inactive.  Within  the 
bark  there  is  a  bark-forming  tissue,  which  gives  alternate 
layers  of  active  and  inactive  tissue.  The  latter  was  also 
found  to  have  the  property  of  being  impervious  to  hydrogen 
peroxide. 

The  activity  of  the  woods  is  increased  in  all  cases  by 
exposure  to  strong  light,  and  observations  on  the  spectrum 
showed  that  the  blue  end  was  particularly  active. 

The  increased  activity  disappears  on  keeping  the  speci- 
mens after  exposure  in  the  dark. 

Eesinous  substances  extracted  from  a  number  of  woods 
were  found  to  be  all  more  or  less  active.  Para-abietic  acid 
was  prepared  and  found  to  be  particularly  active.  It  is 


Action  of  wood  on  photographic  plate  in  the  dark  (W.  J.  Eussell, 
Phil.  Trans.  B.  197—281). 


CELLULOSE  AS  A  CHEMICAL  INDIVIDUAL  75 

well  known  that  this  body  shows  the  phenomenon  of  aut- 
oxidation,  which  is  no  doubt  associated  with  its  unsaturated 
constitution. 

The  fossil  resins  show  slight  activity ;  coal  also  shows 
activity,  and  attempts  were  made  to  apply  this  to  the 
identification  of  different  types  of  coal. 

Woods  were  exhaustively  treated  with  resin  solvents,  but 
were  found  to  be  still  active,  and  the  evidence  goes  to  show 
that  we  are  dealing  with  a  definite  property  of  the  ligno- 
celluloses. 

It  is  to  be  noted  that  a  short  exposure  to  steam  or  to 
chlorine  gas  renders  the  wood  substance  inactive. 

The  action  is  arrested  in  an  atmosphere  of  carbonic  gas, 
but  is  stimulated  by  the  presence  of  oxygen. 

Experiments  in  which  the  active  substance  in  sufficient 
mass  was  swept  with  a  stream  of  air,  and  the  current  of  air 
afterwards  made  to  act  upon  a  photographic  plate  at  some 
distance,  showed  that  the  active  substance  could  be  carried 
forward. 

It  was  also  found  that  diaphragms  carrying  any  substance 
capable  of  absorbing  and  destroying  hydrogen  peroxide 
arrested  the  action. 

The  investigation  is  still  at  this  empirical  stage.  Eussell 
has  left  an  interesting  legacy  of  highly  suggestive  observa- 
tions, and  the  matter  invites  further  investigation,  as  the 
exploration  of  the  causes  is  calculated  to  throw  a  very 
important  light  on  the  natural  chemical  equilibrium  of  the 
ligno-celluloses. 


CHAPTEK  III 

WOOD  PULPS  IN  RELATION  TO  SOURCES  OF  SUPPLY  :  FOREST 
TREES  AND  FORESTRY 

THE  use  of  wood  pulp  as  a  raw  material  for  the  manu- 
facture of  paper  is  of  comparatively  recent  origin,  its 
commercial  application  for  this  purpose  dating  from  1869, 
when  about  60  tons  of  mechanical-ground  wood  pulp 
were  exported  from  Norway  to  England.  In  the  following 
year  the  quantity  rose  to  500  tons,  and  from  that  year 
onward  the  industry  has  grown  by  leaps  and  bounds,  the 
total  amount  of  wood  pulp  imported  in  1909  being  over 
500,000  tons. 

At  the  present  rate  of  consumption  of  wood  for  paper- 
making,  the  devastation  of  forest  areas  has  become  so 
serious  a  matter  that  the  Governments  of  the  various 
countries  in  which  these  forests  exist  are  taking  vigorous 
steps  in  the  first  instance  to  prevent  their  absolute  destruc- 
tion, but  further  to  secure  a  systematic  upkeep. 

It  is  very  difficult  to  arrive  at  accurate  figures  repre- 
senting the  world's  production  of  wood  pulp ;  but  from  the 
semi-official  published  returns  an  approximate  estimate  may 
be  obtained.  In  dealing  with  these  returns  it  is  to  be  noted 
that  the  systems  of  measurement,  the  methods  of  recording 
results,  and  the  tabulation  of  the  records  are  different  in 


SOURCES   OF   SUPPLY 


77 


each  country,  and  such  figures  are  of  little  service  unless 
reduced  to  some  common  standard  of  measurement. 

TABLE  I.i 

SHOWING   ANNUAL    PRODUCTION    OF   WOOD   PULP    FOR   VARIOUS 
COUNTRIES,  CALCULATED  ON  THE  AIR  DRY  BASIS  (1907 — 1908). 


Country. 

Mechanical  pulp. 
Air  dry  tons. 

Chemical  pulp. 
Air  dry  tons. 

Total  annual 
production. 

Germany  . 
Norway     . 
Sweden 
Finland     . 
America    . 
Canada 

315,000 
421,000 
78,000 
69,000  , 
868,000 
565,000 

320,000 
270,000 
510,000 
52,000 
988,000 
172,000 

635,000 
691,000 
588,000 
121,000 
1,856,000 
737,000 

2,316,000 

2,312,000 

4,628,000 

The  most  convenient  unit  which  may  be  taken  as  the 
basis  of  measurement  for  comparison  is  the  "  cord"  of  wood, 
consisting  of  a  number  of  short  logs,  each  4  feet  long,  piled 
up  in  a  space  8  feet  long  and  4  feet  high.  Such  a  pile  of 
logs  measuring  8  feet  X  4  feet  X  4  feet  =  128  cubic  feet, 
is  called  a  "  cord  "  of  wood.  The  unit  of  weight  may  be 
taken  in  terms  of  the  English  ton  of  2,240  Ibs.  (See 
p.  85.) 

These   figures   do   not   convey   even    in    such    concrete 


1  The  sources  of  information  from  which  Table  I.  has  been  com- 
piled are  as  follows: — Germany:  Figures  given  by  Dr.  Kirchner  in 
"  Wochenblatt,"  1907.  Scandinavia:  Eeport  British  Wood  Pulp 
Association,  1909.  America  :  "  Wood  Used  for  Pulp,"  U.S.A.  Bulletin. 
Canada:  "Wood  Pulp  in  Canada,"  official  report,  Geo.  Johnston. 
Finland  :  Paper  Trade  Revieiv,  1908. 


78  WOOD   PULP  AND  ITS   USES 

form  any  accurate  picture  of  the  extensive  cutting  opera- 
tions which  are  going  on,  for  the  manufacture  of  wood  pulp. 
Some  idea  may  possibly  be  obtained  by  attempting  to 
estimate  the  number  of  standing  trees  felled  to  supply  the 
quantity  of  pulp  wood  mentioned.  This  will  vary  in 
different  countries  according  to  the  nature  and  size  of  the 
trees.  According  to  general  practice,  the  large  trees  are 
reserved  for  lumber  and  the  manufacture  of  boards  for 
building  purposes,  so  that  the  trees  used  for  pulp  may  be 
taken  at  an  average  diameter  of  about  9  inches. 

The  ordinary  spruce  or  pine  tree  of  this  diameter  will 
yield  three  logs,  each  16  feet  long,  and  when  the  logs  are 
cut  into  4-feet  lengths,  twelve  pieces. 

The  number  of  pieces  required  to  give  a  piled  cord  of 
128  cubic  feet  capacity  is  about  sixty,  so  that  for  each  cord 
five  trees  would  be  necessary. 

Assuming  that  1  ton  of  dry  chemical  pulp  is  obtained 
from  2J  cords  of  wood,  and  1  ton  of  mechanical  pulp  from 
1J  cords  of  wood,  then  the  total  quantity  of  timber  to  be 
cut  for  the  production  of  the  amount  of  wood  pulp  shown 
in  Table  I.  would  be  about  eight  million  cords. 

A  certain  proportion  of  the  trees  cut  are  faulty  and 
decayed,  while  some  are  lost  in  transit  from  the  forest  to 
the  pulp  mill,  so  that  the  actual  number  felled  for  pulp 
wood  is  somewhat  in  excess  of  the  quantity  indicated.  In 
relation  to  forestry  and  the  destruction  of  forests,  we  have 
to  consider,  in  addition  to  the  wood  cut  for  pulp,  the  number 
of  trees  required  for  timber,  and  the  sum  of  these  figures 
reaches  formidable  dimensions. 

Forestry. — The  available  forest  areas  of  different  countries 
have  been  given  by  Schlich  as  follows  : — 


SOURCES  OF  SUPPLY  79 

TABLE  II. 

Country.  Acres  (millions). 

Canada     ..        .        .        . .       .        .        .  800 

America    ...         ,         .         .         .         .  400 

Kussia      .....       .         .         .         .  500 

Austria-Hungary 46 

Germany  .......  35 

Sweden 49 

Spain        .......  21 

Norway     .......  17 

France 23 

Italy          .....  .10 

Eoumania         ......  5 

Great  Britain 3 

The  preservation  of  the  forests  in  wood-producing 
countries  is  thus  an  acute  problem,  and  of  recent  years  the 
subject  of  afforestation  has  aroused  considerable  interest 
in  England,  especially  in  regard  to  the  industrial  possi- 
bilities ;  but  incidentally  also  as  affecting  rainfall,  and 
therefore  general  agriculture.  One  of  the  most  important 
questions,  therefore,  in  this  connection  is  the  calculation  of 
area  necessary  to  supply  a  mill  continously  with  wood 
pulp. 

For  example,  What  area -of  land  planted  with  spruce  and 
hard  woods  would  be  necessary  to  supply  a  mill  having  an 
output  of  300  tons  of  newspaper  per  week  ? 

This  quantity  of  paper  would  require  200  tons  of  mechani- 
cal pulp  and  100  tons  of  sulphite  pulp  per  week,  amounting 
to  an  annual  supply  on  a  basis  of  fifty  weeks'  work,  of 
10,000  tons  mechanical  pulp  and  5,000  tons  sulphite  pulp. 


80  WOOD   PULP  AND   ITS  USES 

Taking  1 J  cords  of  wood  as  the  quantity  required  for  1  ton 
of  mechanical  pulp  and  2£  cords  of  wood  for  1  ton  dry 
sulphite  pulp,  the  annual  supply  of  wood  necessary  is 
12,500  cords  for  mechanical,  and  11,250  cords  for  sulphite 
pulp,  or  an  approximate  total  of  25,000  cords. 

The  actual  amount  of  spruce  or  pulp-producing  woods 
per  acre  varies  enormously  in  different  countries  and  in 
different  localities,  and  it  is  difficult  to  fix  an  average.  In 
thickly  wooded  areas  which  have  not  been  cut  over,  the 
quantity  frequently  reaches  40  to  50  cords  per  acre  ;  but  on 
timber  lands  which  have  been  continuously  "  operated  "  the 
amount  may  not  exceed  3  to  4  cords. 

Taking  10  cords  to  the  acre  as  a  moderate  and  probable 
allowance,  then  in  the  above  case  2,500  acres  would  be 
required  to  give  the  wood  pulp  necessary  for  one  year.  If 
the  total  forest  area  was  100,000  acres,  then  the  timber 
available  would  be  sufficient  for  forty  years'  supply.  During 
that  period  the  spruce  largely  reproduces  itself,  so  that  by 
progressive  and  careful  management  of  the  forest  in  the 
matter  of  planting  and  reproduction,  an  area  of  100,000 
acres  should  afford  a  perpetual  supply  to  the  mill  quoted. 

Mr.  Parker  Smith,  in  a  paper  entitled  "  Afforestation," 
read  before  the  English  Paper  Makers'  Association,  1910, 
says  that  at  the  Canadian  Convention  one  manufacturer 
stated  he  could  run  his  mill  perpetually  on  a  grant  of 
25,000  acres,  which  would  permit  of  his  cutting  on  a  forty 
years'  rotation,  and  yield,  on  a  basis  of  10  tons  of  pulp  per 
acre,  a  total  of  6,000  tons  annually. 

Comparing  this  statement  with  the  one  already  quoted, 
and  assuming  that  the  6,000  tons  consisted  of  4,000  tons 
mechanical  pulp  and  2,000  tons  sulphite  pulp,  the  weekly 


SOURCES   OF   SUPPLY  81 

production  of  the  mill  works  out  at  120  tons  of  paper  per 
week,  requiring  10,000  cords  of  pulp  wood.  On  this  com- 
putation the  manufacturer  referred  to  was  calculating  the 
quantity  of  pulp  wood  per  acre  to  be  16  cords. 

Pinchot,  the  well-known  American  forestry  expert,  has 
carried  out  some  valuable  and  elaborate  experiments  on  the 
subject  of  the  growth  of  spruce.  A  large  area  of  forest  land 
was  carefully  examined  for  the  nature  of  the  timber,  its 
condition,  growth,  and  other  important  information. 
Careful  attention  was  given  to  the  rate  of  the  growth  of  the 
timber  both  in  the  virgin  forest  and  also  on  areas  which 
had  been  previously  "operated"  for  timber.  The  data 
obtained  in  this  investigation  enabled  Mr.  Pinchot  to  con- 
struct tables  showing  the  amount  of  timber  which  could  be 
cut  from  the  forest,  and  the  number  of  years  which  would 
elapse  before  an  equal  quantity  of  timber  could  be  cut 
from  the  same  area.  One  example  of  this  will  be 
sufficient : — 

A  man  owns  100,000  acres,  yielding  on  an  average  7 
cords  per  acre  of  spruce  10  inches  and  over  in  diameter. 
How  much  can  he  cut  annually  if  he  wishes  to  obtain 
a  sustained  annual  yield,  and  how  soon  can  he  return 
to  the  portion  cut  over  the -first  year,  and  cut  the  same 
amount  of  timber  about  the  same  diameter  limit  as  at 
first? 

In  the  tables  published  by  Mr.  Pinchot  the  total  amount 
of  wood  with  a  diameter  limit  of  10  inches  appears  to  be 
100,000  X  7  cords  =  700,000  cords,  while  the  same  yield 
of  pulp  wood  could  be  obtained  after  thirty-seven  years. 
The  area  to  be  operated  annually  will  be  100,000  -7-  37, 
namely,  2,700  acres.  The  annual  cut  of  wood  will  be 

W.P.  G 


82  WOOD   PULP  AND  ITS  USES 

700,000  -=-  37  =  19,000  cords.  This  illustration,  taken  at 
random  from  the  experiments  of  Mr.  Pinchot,  coincides 
closely  with  the  other  cases  quoted,  and  if  the  diameter 
limit  was  reduced  to  9  inches  a  larger  annual  cut  would 
have  been  obtained. 

The  problem  of  forestry  has  been  studied  and  worked 
out  on  a  successful  commercial  basis  in  several  European 
countries.  In  Saxony,  for  example,  the  State  control  of  an 
area  of  430,000  acres  has  resulted  in  a  large  and  profitable 
turnover,  giving  a  steady  revenue  of  increasing  amount,  as 
well  as  constant  employment  to  skilled  labour.  In  fifty 
years  the  State  has  realised  the  sum  of  i'40,000,000,  and 
the  careful  scientific  methods  of  cutting,  aided  by  proper 
attention  to  means  for  reproduction,  has  improved  the 
quantity  and  quality  of  available  timber.  At  a  recent 
meeting  of  the  Canadian  Forestry  Convention  it  was  shown 
that  the  amount  of  standing  timber  in  the  State  of  Saxony 
had  increased  by  16  per  cent.,  even  during  the  period  of 
constant  cutting,  and  that  the  net  revenue  was  22s.  as 
compared  with  4s.  fifty  years  previously. 

The  same  satisfactory  results  are  shown  by  other 
countries  in  which  forestry  as  a  commercial  undertaking 
has  been  treated  seriously. 

In  England  the  matter  has  been  under  consideration 
for  some  time,  and  the  Report  of  the  Committee  on  Re- 
afforestation, issued  in  1909,  is  full  of  useful  and 
suggestive  evidence.  It  is  interesting  to  note  that  the 
waterworks  committees  of  several  large  municipal  corpora- 
tions, such  as  Liverpool,  Manchester  and  Birmingham, 
have  taken  up  the  question,  primarily  for  the  purpose  of 
conserving  the  rainfall  incidental  to  the  watershed  under 


SOUECES  OF   SUPPLY  83 

control,  and  then  turning  the  large  areas  thus  acquired 
for  maintaining  the  water  supply  to  useful  account  by 
planting  trees. 

The  attractiveness  of  afforestation  in  the  United  Kingdom 
is  clearly  shown  by  the  Committee's  report.  The  con- 
clusions arrived  at  are  briefly— 

1.  Afforestation  is  a  practicable  scheme,   the   available 
area  in  the  United  Kingdom  being  9,000,000  acres. 

2.  The  best  rotation  to  secure  a  continuous  yield  of  wood 
requires  150,000  acres  to  be  dealt  with  annually. 

3.  Afforestation    is    a    productive    investment    for    the 
development    of    the    full    scheme,    for    9,000,000    acres 
would   require   an    annual   sum   of  £2,000,000.     The  net 
deficit   would   be   £90,000   in   the  first   year,  rising   pro- 
gressively to  £3,131,250   in   the   fortieth   year,  in  which 
period  the  forest  becomes  more  than  self  supporting. 

4.  After  eighty  years  the  net  revenue  at  present  prices 
for  timber  should  be  £17,500,000.     This  represents  3J  per 
cent,  on  the  net  cost  calculated  at  accumulating  compound 
interest  at  3  per  cent. 

5.  Afforestation  creates  a  new  industry  which  does  not 
compete  with  private  enterprise,  and  would  afford  permanent 
employment  to  one  man  per  hundred  acres,  and  temporary 
employment  to  a  large  number  of  men  during  the  winter 
months. 

Cost  of  Afforestation. — The  Committee  gives  the  following 
example  :— 

We  assume,  as  regards  expenses,  that  :— 

1.  150,000  acres  are  annually  afforested  for  sixty  years, 
and  that  the  cost  of  the  freehold  and  expenses  of  afforesta- 
tion amount  to  £13  6s.  Sd.  per  acre. 

G  2 


84  WOOD  PULP  AND  ITS  USES 

2.  The  annual  outlay  for  administrative  expenses  is  4s. 
per  acre. 

3.  One-third  of   the  area  is  worked  on  a   forty  years' 
rotation,  and  two-thirds  on  an  eighty  years'  rotation. 

4.  The  cost  of  re-afforestation  is  £6  10s.  per  acre ;  and 

5.  The  rate  of  interest  is  3  per  cent,  per  annum. 
We  further  assume,  as  regards  receipts,  that — 

1.  Thinnings  take  place  at  the  end  of  the  twentieth  year, 
and  at  the  end  of  each  successive  decade  from  the  date  of 
planting. 

2.  The  net  receipts  for  the  initial  thinnings  amount  to 
2s.  6d.  per  acre,  and  for  the  succeeding  thinnings  are  at 
the  rate  of  £3,  £6,  £9,  £12,  and  £15  per  acre  respectively. 

3.  The   area   which   is   afforested   on   an   eighty  years' 
rotation  yields  £175  per  acre  on  being  clear-felled  at  the 
end  of  eighty  years. 

4.  The  area  which  is  afforested  on  a  forty  years'  rotation 
yields  £60  per  acre  on  being  clear-felled  at  the  end  of  forty 
years ;  and 

5.  The  rate  of  interest  is  3  per  cent,  per  annum. 

The  annual  deficit  on  the  transaction  rises  from  £90,000 
in  the  first  to  £3,131,250  in  the  fortieth  year ;  in  the 
forty-first  and  up  to  the  sixtieth  year  the  forest  becomes 
practically  self-supporting  ;  in  the  sixty-first  year,  and  sub- 
sequently, an  increased  revenue  is  received,  but  it  is  not 
until  the  eighty-first  year  that  the  full  results  are  obtained  ; 
in  this  year  and  subsequently  an  approximate  equalised 
revenue  of  £17,411,000  per  annum  being  realised.  Further 
calculations  show  that  the  value  of  the  property  would  then 
be  £562,075,000,  or  £106,993,000  over  and  above  the  cost 
of  its  creation.  The  equalised  annual  revenue  of  £17,411,000 


SOURCES  OF  SUPPLY  85 

represents  a  yield  of  £3  16s.  6^/.  (approximately)  per  cent, 
on  the  excess  of  accumulated  charges  over  receipts. 

Measurement  of  Pulp  Wood. — The  systems  for  measuring 
wood  used  in  the  manufacture  of  pulp  differ  in  the  several 
countries. 

Scandinavia. — The  wood  is  measured  in  terms  of  fathoms 
or  of  cubic  metres,  the  price  paid  for  raw  material  being 
determined  by  reference  to  a  table  showing  the  sum  to  be 
paid  for  logs  of  varying  lengths  and  varying  diameters. 

One  fathom  =       6  feet. 

One  cubic  fathom  =  216  cubic  feet. 
Germany. — Wood  is  usually  measured  in  Germany  and 
other  Continental  countries  by  the  cubic  metre.     A  cubic 
metre  of  piled  logs  is  called  a  Eaummeter,  the  amount  of 
actual  solid  wood  contained  in  the  pile  being  known  as  a 
Festmeter,  the  relation  between  these  measurements  being 
One  Kaummeter  =  0'77  Festmeter. 
One  cubic  metre  =  35*314  cubic  feet. 

America. — Many  systems  are  in  use,  the  most  common 
being  the  measurement  by  cords.     A  cord  is  a  pile  of  logs 
feet  long,  4  feet  wide  and  4  feet  high. 

One  cord  piled  logs  =  128  cubic  feet. 

Canada. — Measurements  are  also  based  upon  the  use  of 
a  cord  of  wood,  in  two  ways,  the  first  being  the  piled  cord 
of  128  cubic  feet  and  the  second  a  solid  cord  which  is  the 
amount  of  solid  wood  contained  in  a  piled  cord,  the  relations 
being  as  follows  : 

*0ne  piled  cord  =  128  cubic  feet  in  the  whole  pile. 
One  solid  cord  =  115  cubic  feet  of  solid  wood. 


86  WOOD  PULP  AND  ITS  USES 

This  measurement  of  a  solid  cord  has  been  estab- 
lished by  the  government  of  the  province  of  Ontario, 
and  was  arrived  at  by  means  of  a  large  number  of 
special  experiments  carried  out  for  the  purpose  of  estab- 
lishing a  common  standard  of  measurement.  It  does 
not  represent  accurately  the  total  amount  of  solid  wood 
in  an  ordinary  cord  of  128  cubic  feet,  but  it  is  a  figure 
which  has  been  selected  as  the  standard  for  the  payment 
of  dues. 

In  the  province  of  Quebec  a  cord  of  pulp  wood  is  con- 
sidered equal  to  600  feet  board  measure,  which  relation  was 
determined  by  a  series  of  elaborate  tests  instituted  for 
finding  the  amount  of  useful  timber  obtained  from  logs 
intended  for  lumber.  This  relation  is  used  as  a  basis  for 
calculating  payments  due  to  government,  and  does  not 
necessarily  represent  the  true  equivalent,  which  varies 
according  to  the  size  of  the  log. 

The  true  measurement  of  the  amount  of  wood  in  the  logs 
is  best  secured  by  determining  the  actual  cubical  contents 
of  each  log  separately.  By  this  means  all  errors  due  to 
methods  of  piling  the  logs  in  stacks  or  to  the  varying 
lengths  of  the  logs,  is  easily  avoided. 

The  importance  of  this  question  is  easily  shown  in  the 
following  test  made  by  an  expert. 

Forty-two  logs,  each  16  feet  long,  were  piled  up  carefully 
in  a  rack,  the  measurement  of  the  wood  being  exactly  three 
piled  cords  or  384  cubic  feet.  The  16  feet  logs,  after  being 
measured  and  piled,  were  cut  in  half  and  again  piled.  The 
stack  was  measured  and  then  the  logs  were  again  halved, 
giving  pieces  4  feet  long,  which  were  stacked  up  and 
measured.  Finally  the  pieces  were  reduced  to  a  length 


SOURCES  OF  SUPPLY 


87 


of  2   feet,    and   the   process   of    stacking  and   measuring 
repeated.     The  results  are  set  out  in  Table  I. 


TABLE  I. 


No.  of 
pieces. 

Length, 
feet. 

Dimensions  of  pile. 

No.  of 
piled  cords. 

Ratio. 

42 

16 

16  X  16  X  4 

3-00 

100 

84 

8 

IX     6x7-5 

2-81 

93-7 

168 

4 

4  X  12  X  7-16 

2-69 

89-7 

336 

2 

2  X  12  X  13-83 

2-59 

86-3 

The  effect  of  the  closer  packing  rendered  possible  by  the 
reduction  of  length  in  the  log  is  plainly  shown  in  this  table. 
Thus  100  piled  cords  of  wood  measured  in  16  feet  lengths 
only  measured  89*7  when  reduced  to  4  feet.  The  latter  is 
a  customary  unit  of  measurement  for  pulp  wood.  Even  in 
the  case  of  wood  cut  in  8  feet  or  4  feet  lengths  there  would 
be  a  difference  of  four  cords  in  the  measurement,  according 
to  the  length  into  which  the  logs  are  cut.  This  figure  will 
naturally  vary  with  different  logs,  and  cannot  be  accepted 
as  being  applicable  to  all  kinds  of  wood  whether  of  large  or 
small  diameter. 

The  practical  effect  is  also  shown  in  Table  II. 

TABLE  II. 


Length  of 
pieces. 
Feet. 

Piled  cords 
obtained 
from  100 
solid  cords. 

No.  of  pieces 
required  to 
give  piled 
cord. 

Weight  of  a 
piled  cord. 
Ibs. 

Extra  16  ft.  logs 
required  to  give 
the  piled  cord  of 
stated  lengths. 

No.  of 
cubic  feet 
in  piled 
cord. 

16 

137 

14 

3,355 

0 

84-3 

8 

128 

30 

3,580 

1 

90-0 

4 

122 

61 

3,740 

li 

94-0 

2 

118 

129 

3,880 

2 

97-0 

88 


WOOD  PULP  AND  ITS  tJSES 


This  table  is  interesting  as  showing  the  exact  result,  in  a 
practical  manner,  of  reducing  the  length  of  the  log,  the 
difference  being  shown  not  only  in  the  weight  of  the  wood, 
but  also  in  the  very  concrete  fact  that  an  extra  log  or  two 
is  required  to  make  up  the  reduction. 

TABLE  OF  EQUIVALENTS. 


Cubic 
fathoms. 

Cubic 
feet. 

Cubic 
metres. 

Cords. 

One  cubic  fathom  is 

— 

216 

6-113 

1-0687 

One  cubic  foot  is    . 

0-00463 

— 

0-283 

0-00781 

One  cubic  metre  is 

0-163 

35-314 

— 

0-276 

One  cord  is     . 

0-5926 

128 

3-6224 

— 

WOOD  PULP  TREES. 

The  chief  woods  used  for  the  manufacture  of  pulp  are  the 
species  of  spruce,  fir  and  pines  for  sulphite  and  mechanical 
pulps,  the  aspen,  poplar  and  other  deciduous  trees  for  soda 
pulps.  The  conifers  are  also  used  for  the  manufacture  of 
soda  and  sulphate  pulps.  For  wrappers  and  fibre  papers, 
hemlock  is  used  in  considerable  quantity. 

The  following  is  an  alphabetical  list  of  common  woods, 
many  of  which,  however,  find  no  place  at  present  in  the  wood 
pulp  industry.  These  are  printed  in  italics  in  the  name 
column. 


SOURCES  OF  SUPPLY 


Common  name. 

Botanical  name. 

German. 

S£ 

11 

CO  6C 

Weiglit  of 
cubic  foot 
in  Ibs-  | 

Acacia     . 

Robinia  pseudacacia 

Schotendorn 

•73 

45-7 

Alder       . 

Alnus  glutinosa 

Gemeine-eiie 

(Roth-erle) 

•46 

29-0 

Ash 

Fraxinus  excelsior 

Weiss-  esche 

•65 

40-8 

„     Mountain 

Ash      . 

Pyrus  aucuparia 

Eber-esche 

•54 

34-0 

Aspen     . 

Populus  tremula 

Zitter-pappel 

(Aspenholz) 

•50 

31-3 

Balsam  . 

Abies  Fraseri 

•36 

22-2 

Basswood 

Tilia  Americana 

Linde 

•45 

28-2 

Seech 

Fagus  silvatica 

Rotbuche 

•75 

46-8 

Birch       . 

Betula  alba 

Birken-holz 

•64 

40-0 

Chestnut  . 

Castanea  sativa 

Kastanje 

•45 

28-1 

Cottomvood 

Populus  monilifera 

Wollpappel 

•39 

24-2 

Crack  Willow  . 

Salix  fragilis 

Bruchweide 

•45 

28-3 

Cypress    . 

Taxidium  distichum 

Cypresse 

•45 

28-3 

Elm         .       -. 

Ulmus  campestris 

Steinlinde  (Roth- 

ruster) 

•69 

43-3 

Fir 

Picea  excelsa 

Fichte.  Fohre 

•49 

30-0 

,,    Silver  Fir 

(India) 

Abies  pindrow 

Tannenholz-Tanne 

•46 

29-0 

„    Silver  Fir 

(Europe) 

Abies  pectinata 

Tannelholz-Tanne 

•49 

30-0 

Hemlock 

Abies  canadiensis 

Schierlingstanne 

•42 

26-4 

Hornbeam 

Carpinus  betulus 

Weissbuche 

(Hagebuche) 

•72 

45-0 

Larch 

Larix  Europea 

Lorche 

•74 

46-1 

Maple 
Paper  Birch     . 

Acer  dasycarpum 
Betula  papyrifera 

Ahorn 

•52 
•60 

32-8 
37-1 

Pines    •   . 

Kiefer.  Nadelholz 

Black  Pine    . 

Pinus  austriaca 

Schwarzfohre 

•57 

35-4 

White  Pine  . 

Pinus  strobus 

Wehmuthskiefer 

•38 

24-0 

Pitch  Pine     . 

Pinus  palustris 

Gelbkiefer 

•70 

43-6 

Poplar     . 

Populus 

Pappel 

•40 

25-6 

White  Poplar 

Populus  alba 

Silberpappel 

•48 

30-0 

Black  Poplar 

Sallow  (  Willow) 

Populus  nigra 
Salix  caprsea 

Schwarzpappel 
Sahlweide 

•48 
•55 

30-0 
35-0 

Sandalwood 

Santalum  album 

Santalholz 

•98 

60-0 

Spruce    . 

Picea  excelsa 

Fichte  (Tanne) 

•42 

26-7 

White  Spruce 

Picea  alba 

Weisstanne 

•40 

25-2 

Tamarac 

Larix  americana 

Lorche 

•62 

38-9 

Willow    . 

Salix  nigra 

Weide 

•44 

27-7 

Coniferse.     Cone-bearing  trees 
Deciduous  or  leaf-bearing  trees 


Nadelholz. 
Laubholz. 


90  WOOD  PULP  AND  ITS  USES 

The  History  of  Mechanical  Wood  Pulp. — The  possibility 
of  using  wood  for  papermaking  seems  to  have  been 
deduced  from  the  Reaumur  observation  that  wasps  build 
their  nests  from  partially  decayed  wood  which  they  obtained 
from  trees  or  timber.  In  1765  J.  C.  Schaffer,  a  priest  in 
Regensburg,  published  a  book  containing  samples  of  paper 
made  from  many  raw  materials,  and  referring  especially  to 
wood,  wrote:  "it  must  be  possible,  though  with  different 
methods,  to  make  paperstuff  from  wood  and  consequently 
use  it  instead  of  the  ordinary  rags  for  papermaking." 

This  is  an  interesting  statement  in  view  of  the  fact  that 
nothing  was  then  known  of  the  use  of  alkalies  or  other 
chemical  agents  for  reducing  fibrous  materials  to  pulp. 

Schaffer  experimented  with  the  material  of  the  wasps' 
nest,  with  sawdust  and  shavings.  From  some  seven  or 
eight  species  of  wood  he  made  excellent  sheets  of  paper, 
having  regard  to  the  means  at  his  disposal.  He  published 
a  second  edition  of  his  book,  entitled,  "  Sarntliche  Papier- 
versuche-Nebst  81  Mustern  und  13  Kupfertafeln,"  in  1772, 
and  enlisted  the  services  of  a  papermaker,  Meckenhauser, 
to  enable  him  to  produce  some  better  results. 

In  1800  Matthias  Koops,  a  Dutchman,  published  a  book 
which  he  printed  on  paper  made  from  straw  pulp  and 
dedicated  to  King  George  III.  He  added  an  appendix  to 
his  work  which  was  printed  on  paper  made  entirely  of  wood 
pulp,  an  idea  suggested  to  him  no  doubt  by  the  work  of 
J.  C.  Schaffer.  Koops  was  a  man  of  some  enterprise,  for  he 
also  issued  a  work  on  paper  made  entirely  from  old  waste 
paper,  this  being  probably  the  first  attempt  to  utilise  old 
waste  material  for  such  a  purpose. 

In  1840  Friedrich  G.  Keller,  a  young  weaver  of  Haynich, 


SOUECES  OF  SUPPLY  91 

in  Saxony,  reading  in  a  scientific  journal  of  the  great 
scarcity  of  rags  as  material  for  papermaking,  resolved  to 
keep  his  eyes  open  for  a  substitute.  In  1843  his  attention 
was  called  to  the  remarkable  paperlike  appearance  of  the 
wasps'  nest,  and  recollecting  that  in  his  school  days  he  had 
ground  down  cherry  stones  on  an  ordinary  grindstone  in 
order  to  make  a  cherry  chain,  he  tried  the  effect  of  holding 
a  piece  of  wood  against  the  revolving  stone.  To  his  great 
delight  the  experiment  was  successful,  and  he  collected  the 
fibres  so  isolated  from  the  wood  and  made  a  minute  piece 
of  paper. 

Keller  continued  his  experiments,  and  in  1844  manu- 
factured about  2  to  3  cwt.  of  pulp,  which  was  beaten  up 
with  rag  pulp  and  made  into  paper.  In  1845  he  parted 
with  the  secret  of  his  process,  and  disposed  of  it  to  Heinrich 
Volter  for  the  sum  of  700  thaler  (£140)  ! 

The  progress  of  the  new  method  was  somewhat  slow,  but 
improvements, including  the  necessary  treatment  for  refining 
the  pulp,  or  removing  the  coarse  chips,  were  introduced, 
and  towards  1860  the  process  was  put  on  a  more  satisfactory 
footing.  In  1862  Yolter  was  awarded  the  medal  of  the 
International  Arts  and  Industries  Exhibition  in  London. 

Between  1862  and  1865  seven  or  eight  pulp  mills  were 
erected  in  Germany  and  Scandinavia  and  the  manufacture 
of  ground  wood  pulp  on  a  large  scale  became  an  accomplished 
fact. 

History  of  Chemical  Wood  Pulp. — The  early  attempts  of 
Koops  in  1800  to  utilise  straw,  and  his  few  experiments 
with  wood  as  substitutes  for  rag,  may  be  regarded  as  the 
starting  point  in  the  history  of  chemical  wood  pulp.  The 
materials  were  probably  boiled  with  some  crude  soda  ley 


92  WOOD  PULP  AND  ITS  USES 

and  subsequently  beaten  into  pulp.  About  this  period  soda 
ash,  caustic  soda,  chlorine  and  bleaching  powder  and  other 
chemicals  had  been  introduced  to  the  manufacturing  world, 
so  that  the  possibilities  for  reducing  vegetable  products  to 
the  condition  of  pulp  were  much  greater. 

In  1857  Houghton  patented  a  process  for  digesting  wood 
with  caustic  soda  at  high  temperatures  in  closed  vessels. 

In  1863,  Tilghmann,  an  American  chemist,  suggested 
the  use  of  a  solution  of  sulphurous  acid  gas.  His  early 
experiments  were  carried  out  in  lead-lined  vessels,  but  the 
work  was  abandoned  owing  to  difficulties  connected  with 
the  construction  of  suitable  digestors. 

As  Tilghmann  was  the  inventor  of  a  process  which  has 
become  the  basis  of  a  large  and  important  industry,  the 
following  precis  of  his  first  patent,  as  given  by  Mr.  A.  D. 
Little,  may  be  quoted  as  having  a  peculiar  interest  :— 

The  process  of  treating  vegetable  substances  which  contain  fibres 
with  a  solution  of  sulphurous  acid  in  water,  either  with  or  without  the 
addition  of  sulphites  or  other  salts  of  equivalent  chemical  properties 
as  above  explained,  heated  in  a  closed  vessel,  under  pressure,  to  a 
temperature  sufficient  to  cause  it  to  dissolve  the  intercellular  incrusting 
or  cementing  constituents  of  said  vegetable  substances,  so  as  to  leave 
the  undissolved  produce  in  a  fibrous  state,  suitable  for  the  manufacture 
of  paper,  paper  pulp,  cellulose,  or  fibres,  or  for  other  purposes,  according 
to  the  nature  of  the  material  employed. 

I  also  claim  as  new  articles  of  manufacture  the  two  products 
obtained  by  treating  vegetable  substances  which  contain  fibres  with  a 
solution  of  sulphurous  acid  in  water,  either  with  or  without  the 
addition  of  sulphites  or  other  salts  of  equivalent  chemical  properties, 
as  above  explained,  heated  in  a  closed  vessel,  under  pressure,  to  a 
temperature  sufficient  to  cause  it  to  dissolve  the  intercellular  or 
incrusting  constituents  of  said  vegetable  substances,  one  of  said 
products  being  soluble  in  water,  and  containing  the  elements  of  the 
starchy,  gummy,  and  saline  constituents  of  the  plants,  and  the 
other  product  being  an  insoluble  fibrous  material,  applicable  to  the 


SOURCES  OF   SUPPLY  93 

manufacture  of  paper,  cellulose  or  fibres,  or  to  other  purposes, 
according  to  the  nature  of  the  material  employed. 

I  also  claim  the  use  and  application ,  in  the  manufacture  of  paper, 
paper  pulp,  cellulose  and  fibres,  of  the  fibrous  material  produced  by 
treating  vegetable  substances  which  contain  fibres  with  a  solution  of 
sulphurous  acid  in  water,  either  with  or  without  the  addition  of 
sulphites  or  other  salts,  of  equivalent  chemical  properties  as  above 
explained,  heated  in  a  closed  vessel,  under  pressure,  to  a  temperature 
sufficient  to  cause  it  to  dissolve  the  incrusting  or  intercellular  con- 
stituents of  said  vegetable  substances. 

I  also  claim  the  use  and  application  of  sulphites  or  other  salts  of 
equivalent  chemical  properties  as  above  explained,  in  combination 
with  a  solution  of  sulphurous  acid  in  water,  as  an  agent  in  treating 
vegetable  substances  which  contain  fibres,  when  heated  therewith  in  a 
close  vessel,  under  pressure,  to  a  temperature  sufficient  to  cause  the 
said  acid  solution  to  dissolve  the  intercellular  or  incrusting  constituents 
of  said  vegetable  substances. 

I  also  claim  the  recovery  and  re-use  of  sulphurous  acid  and  sulphite 
from  the  acid  liquids  which  have  been  digested  on  the  vegetable 
fibrous  substances,  by  boiling  said  liquids  or  neutralising  them  with 
hydrate  of  lime. 

In  1872  Ekman  had  developed  a  process  which  was 
commercially  successful,  and  this  was  introduced  into 
England,  at  Ilford,  Essex,  about  1884,  a  mill  being  erected 
a  few  years  later  at  Northfleet  in  Kent  for  the  treatment  of 
wood  by  means  of  bi-sulphite  of  magnesia. 

In  1876,  Mitscherlich,  a  celebrated  German  chemist, 
experimented  with  sulphurous  acid  and  devised  a  method 
for  converting  wood  into  pulp  by  cooking  under  low  pressure 
for  a  long  period,  producing  a  half-stuff  eminently  suitable 
for  certain  classes  of  paper. 

Numerous  and  extensive  modifications  of  the  original 
Tilghmann  sulphite  process  have  resulted  in  the  evolution  of 
an  industry  typical  of  modern  chemical  engineering.  Such 
modifications  refer  to  details  of  working,  more  particularly 


94  WOOD   PULP  AND   ITS  USES 

to  the  type  of  boiler  or  digestor,  to  economy  in  the  amount 
of  sulphur  used,  to  improving  or  varying  the  quality  of 
the  pulp,  and  to  general  efficiency,  and  are  of  subordinate 
historical  interest. 

There  has  been  a  good  deal  of  controversy  as  to  the 
priority  of  original  invention  of  this  most  important  indus- 
trial development.  It  has  always  appeared  to  us  that  while 
Tilghmann  is  the  pioneer  from  the  technological  stand- 
point, on  the  clear  and  specific  claims  of  his  patent  above 
set  forth,  the  practical  and  industrial  pioneers  were  George 
Fry  and  his  collaborator  Ekman.  Some  years  in  advance 
of  the  bi-sulphite  process  (1869)  Fry  investigated  the  action 
of  water  only  at  high  temperatures  and  pressures,  paying 
particular  attention  to  the  volatile  by-products  of  the 
complex  reactions ;  and  in  this  investigation  secured  the 
collaboration  of  the  late  Greville  Williams,  who  identified 
furfural  amongst  the  products  of  decomposition  of  the  ligno- 
cellulose. 

Finding  that  the  resolution  of  the  wood  under  these 
conditions  was  limited  by  the  influences  of  oxidation  and 
condensation,  it  was  then  suggested  by  Fry  to  Ekman,  who 
had  become  associated  with  these  researches,  to  seek  for  a 
new  chemical  condition  to  antagonise  these  influences.  In 
this  path  of  logical  though  empirical  evolution  this  group 
of  pioneers  may  be  held  to  have  independently  discovered 
the  bi-sulphite  process  ;  and  Ekman,  with  George  Fry,  had 
the  satisfaction  of  working  the  process  to  an  industrial  and 
commercial  success  at  Bergvik,  Sweden,  then  at  Ilford,  and 
lastly  at  Northfleet. 

The  following  is  a  chronological  list  of  inventions  for  the 
preparation  of  pulp  from  wood  by  chemical  reactions  : — 


SOUECES  OF  SUPPLY 


95 


Year. 

Name. 

Process. 

1840 

Payen 

Nitric  Acid 

1852 

Coupler  &  Mellier 

Soda 

1853 

Watt  &  Burgess 

Alkalis 

1855 

Jullion 

Alkaline  salts 

1857 

Houghton 

Alkalis 

1861 

Barre  &  Blondel 

Dilute  acids 

1864 

Bachet  &  Machard 

Acids 

1866 

Tilghmann 

Sulphurous  Acid  and  salts 

1867 
1870 

Fry 
Ekman 

Water  at  high  temperatures 
Magnesium  Sulphite 

1870 

Dresel 

Soda 

1871 

E.  Mitscherlich 

Sulphurous  Acid  and  salts 

1872 

Ungerer 

Soda 

1872 

Eotter-Kellner 

Sulphurous  Acid  and  salts 

1880 

Cross 

Water  and  neutral  sulphites 

1881 

Francke 

Sulphurous  Acid  and  salts 

1882 

Pictet  &  Brelay 

Sulphurous  Acid 

1882 

Graham 

Sulphurous  Acid  and  salts 

1883 

Blitz 

Alkalis  and  sulphites 

1883 

Dahl 

Sulphates  and  sulphides 

1885 

Kellner 

Electrolytic  process 

1890 

Lifschutz 

Nitric  and  sulphuric  acids 

1894 

Cross 

Nitric  Acid  —  dilute 

CHAPTEK  IV 

THE  MANUFACTURE  OF  MECHANICAL  WOOD  PULP 

THE  term  "mechanical"  or  "ground"  wood  pulp  is 
applied  to  pulp  which  has  been  prepared  by  a  mechanical 
process.  The  principle  of  the  operation  is  merely  the  dis- 
integration of  wood  into  fibres  by  means  of  a  grindstone, 
the  wood  being  brought  into  contact  with  the  stone  as  it 
revolves.  The  conditions  of  manufacture  are  capable  of 
considerable  modification  so  that  various  grades  and 
qualities  of  product  are  possible. 

Preparation  of  Wood. — The  logs  of  wood,  which  have 
been  brought  to  the  mill  from  the  timber  limits  or  other 
sources,  and  which  vary  in  length  from  10  to  16  feet,  are 
first  reduced  to  a  uniform  length  of  24  inches  by  means  of 
large  circular  saws. 

The  arrangements  in  a  modern  pulp  mill  for  handling 
the  logs  and  preparing  them  for  conversion  into  pulp  call 
for  considerable  skill  and  attention  in  order  to  produce  the 
optimum  result  at  minimum  cost. 

The  short  pieces  of  wood  are  automatically  conveyed  to 
the  "  barking  "  room  and  there  deprived  of  the  outer  bark. 
The  machine  used  for  this  purpose  consists  of  a  heavy 
circular  iron  disc  enclosed  in  a  strong  casing.  The 
disc  is  provided  with  three  knives  projecting  from  the 
surface  of  the  disc  in  such  a  manner  that  when  the  short 
pieces  of  wood  are  pressed  against  the  surface  of  the  disc, 


MECHANICAL  WOOD  PULP  97 

as  it  revolves,  they  are  completely  denuded  of  the  bark 
itself.  A  considerable  proportion  of  wood  is  lost  in  this 
process,  the  amount  varying  from  15  to  25  per  cent., 
according  to  the  size  and  condition  of  the  logs.  The  bark 
is  generally  burnt  in  special  ovens  and  utilised  as  fuel. 

The  clean  pieces  of  wood  may  be  employed  for  the  manu- 
facture of  either  mechanical  or  chemical  wood  pulp  and 
in  practice  the  pieces  are  often  sorted  out,  the  clean  wood 
free  from  dirt  and  knots  being  reserved  for  chemical  pulp, 
and  the  inferior  wood  being  converted  into  mechanical 
wood  pulp. 

Cold-ground  Pulp. — When  the  wood  is  ground  into  fibres 
in  the  presence  of  a  large  excess  of  water,  a  fine  even  pulp 
of  uniform  quality  is  produced.  This  pulp  is  known  as 
"  cold-ground  "  in  contradistinction  to  "  hot-ground  " 
pulp,  which  is  produced  under  the  condition  of  high  tem- 
perature (infra). 

The  machine  used  for  the  manufacture  of  the  cold  ground 
pulp  consists  of  a  horizontal  grindstone,  usually  60  inches 
in  diameter  and  with  27  inches  breadth  of  face,  mounted 
on  a  heavy  vertical  shaft  and  encased  in  a  strong  cast-iron 
circular  box,  as  shown  in  Fig.  14.  Around  the  circumference 
of  the  box  there  are  a  number  of  recesses  or  "pockets" 
in  which  the  short  2  feet  pieces  of  wood  are  placed. 
The  wood  is  pressed  against  the  surface  of  the  rotating 
grindstone  by  pistons  operating  under  hydraulic  pressure, 
water  being  continuously  applied  to  the  surface  of  the 
stone  so  that  the  disintegrated  fibres  are  carried  away 
from  the  stone  into  storage  reservoirs  for  subsequent 
treatment. 

Hot-ground  Pulp. — When  the  quantity  of  water  flowing 

W.P.  H 


98 


WOOD  PULP  AND  ITS  USES 


to  the  grindstone  is  reduced  to  a  minimum  then  the  tempera- 
ture of  the  mass  in  contact  with  the  stone  rises  rapidly  on 
account  of  the  friction,  and  the  wood  is  thus  ground  to  pulp 


FIG.  14.— View  of  Horizontal  Grinder  (A),  with  Section  (B). 

under  entirely  different  conditions.  The  fibres  are  readily 
torn  away  from  the  wood,  and  produce  a  pulp  which  is  much 
coarser  than  the  cold-ground  pulp,  the  fibres  being  longer. 


MECHANICAL  WOOD   PULP  99 

The  machine  used  for  the  manufacture  of  this  pulp 
consists  of  a  grindstone  mounted  in  a  vertical  position  on  a 
horizontal  shaft,  operated  by  a  water  turbine.  The  stone 
is  enclosed  in  a  circular  iron  casing  provided  with  "  pockets" 
into  which  the  blocks  of  wood  are  placed.  The  pieces  of 
wood  are  forced  against  the  surface  of  the  stone  by  hydraulic 
pressure. 

The  water  is  supplied  to  the  grindstone  in  limited 
quantity,  just  sufficient  being  used  to  prevent  the  pulp 
from  being  burnt  or  spoilt.  The  temperature  frequently 
rises  to  150°  Fahr.,  owing  partly  to  the  greater  pressure  of 
the  wood  against  the  stone,  and  also  by  the  conditions 
under  which  a  limited  supply  of  water  is  used.  Pulp  of 
this  kind  works  freely  on  a  fast-running  news  machine — 
that  is,  as  the  pulp  and  water  flow  on  to  the  wire  of  the 
paper  machine  the  water  drains  quickly  and  freely  through 
the  meshes  of  the  wire,  and  thus  makes  it  possible  for  the 
machine  to  be  operated  at  a  high  speed.  Many  of  the  paper 
machines  used  for  the  manufacture  of  "  news  "  with  pulp  of 
this  character  can  be  run  at  a  speed  of  500  to  600  feet  per 
minute. 

The  quantity  and  quality  of  the  pulp  produced  as  con- 
trolled by  the  conditions  of  grinding  depend  on 

(1)  The  sharpness  of  the  stones  ; 

(2)  The  pressure  applied  to  the  blocks  of  wood  ; 

(3)  The  temperature  of  the  mass  ; 

(4)  The  method  of  applying  the  wood  to  the  stone. 

In  general  terms,  the  quantity  of  the  pulp  is  increased  by 
the  use  of  sharp  stones  and  the  application  of  pressure,  the 
yield  being  highest  with  wood  treated  by  the  hot-ground 
process. 

H2 


100 


WOOD   PULP  AND   ITS  USES 


The  coarseness  of  mechanical  wood  pulp  is  merely  a 
relative  term,  for  it  is  possible  to  have  a  badly-ground  wood 
pulp  well  screened,  giving  a  coarse  material  of  an  even 
uniform  grade,  or,  on  the  other  hand,  a  well-ground  wood 
badly  screened  giving  a  high-class  pulp,  spoilt  by  the 
presence  of  long  chips  or  slivers  which  have  not  been 
removed.  Such  slivers  in  pulp  are  a  fruitful  source  of 
"  breaks  "  on  the  paper  machine,  since  they  locally  reduce 
the  tensile  strength  of  the  web.  Coarse  pulp  of  a  uniform 
grade  does  not  produce  "  breaks,"  but  the  fibres  do  not  lie 
closely  in  the  surface  of  the  paper,  with  the  result  that  a 
large  quantity  of  "fluff"  is  produced  on  the  type  of  the 
rotary  printing  presses. 

The  output  of  a  grinder  is  increased  by  sharpening  the 
stone  and  by  increasing  the  pressure  applied  to  the  blocks 
of  wood.  The  effect  of  using  sharp  stones  is  clearly 
indicated  by  the  following  experimental  results,  obtained 
from  two  or  three  pulp  mills  : — 


Pounds  of  wood  treated  per  hour. 

Ratios. 

Dull  stones. 

Sharp  stones. 

Dull  stones. 

Sharp  stones. 

A 

440 

680 

100 

155 

B 

637 

1061 

100 

167 

C 

628 

830 

100 

138 

The  amount  of  wood  pulp  obtained  from  a  grinder  depends 
chiefly  upon  the  pressure  applied  to  the  wood  in  contact 
with  the  stone,  as  shown  by  Kirchner's  elaborate  experi- 
ments tabulated  in  the  following  table  : — 


MECHANICAL   WOOD  PULP 


101 


Pressure  on  stone. 
Lbs.  per  sq.  in. 

Consumption  of 
power. 
H.P. 

Yield  of  air-dry  pulp 
per  hour. 
Lbs. 

H.P.  required  for 
24  hours  for  1  ton 
air-dry  pulp. 

1 

Mo 

1-25 

86-0 

2 

1-95 

3-30 

56-8 

3 

2-60 

5-15 

47'0 

4 

3-15 

6-60 

44-5 

5 

3-80 

7-92 

44-7 

5-5 

4-05 

8-05 

44-4 

6 

4-40 

8-30 

49-4 

7 

5-0 

7-92 

59-0 

The  effective  work  of  the  stone  under  the  conditions  of 
the  experiment  is  evidently  reached  when  the  pressure  is 
5*5  Ibs.  per  square  inch,  for  at  this  point  the  power  required 
for  a  given  output  is  lowest. 

Kirchner  gives  the  following  interesting  table  showing 
the  influence  of  the  condition  of  the  stones  on  various  kinds 
of  wood : — 

PRODUCTION  OF  PULP  PER  H.P.  PER  24  HOURS  UNDER 
DEFINITE  EXPERIMENTAL  CONDITIONS. 


Wood. 

Well  sharpened  stones 
Lbs.  of  pulp. 

Moderately  sharpened 
stones. 
Lbs.  of  pulp. 

Pine    .... 

6-4 

5-4 

Fir      .         . 

6-8 

— 

Aspen.         .         .        ;. 
Poplar         .        ..      .  k 

8-9 
6-1 

6-3 
5-6 

Lime  .... 

5-9 

5-4 

Birch  .         .         . 

6-7 

— 

Willow 

7-2 

4-6 

Alder. 

i      

6-3 

Oak     .... 

— 

5-1 

In  a  more  complete  series  of  trials  Kirchner  studied  the 
relation  between  the  power  consumed  with  stones  of  varying 


102 


WOOD  PULP  AND  ITS  USES 


degrees  of  sharpness  in  producing  a  stated  quantity  of 
pulp  and  the  pressure  on  the  surface  of  the  stone.  These 
trials  were  conducted  with  the  hot-grinding  process,  and  the 
amount  of  pulp  produced  per  twenty-four  hours  was  taken  as 
100  kilos  (say  220  Ibs.,  or  nearly  2  cwt.),  the  stones  being 
worked  under  conditions  giving  this  output.  Three  stones 
— fine,  medium  and  coarse  grades — were  selected  for  the 
experiment.  The  general  results  obtained  show  that  as 
the  pressure  increased,  the  power  required  decreased  up  to 
a  certain  point,  when  any  further  pressure  at  once  created 
a  demand  for  greater  power.  This  is  admirably  shown  in 
the  diagram  Fig.  15,  where  the  experiments  with  the  three 
classes  of  stone  are  shown  by  the  curves,  A,  fine;  B,  medium; 
C,  coarse. 

The  maximum  output  was  obtained  under  the  following 
conditions : — 


Stone. 

Pressure. 
Lbs.  per  sq.  in. 

Horse-power. 

Output  in 
24  hours. 

A.  Fine 

4-2 

4 

220  Ibs. 

B.  Medium  . 

12-6 

2-4 

220  Ibs. 

C.  Coarse 

8-4 

2 

220  Ibs. 

Excess  of  pressure  is  shown  by  the  sudden  upward  turn  of 
the  curves,  though  with  the  coarse  stone  this  point  has  not 
been  reached. 

The  immersion  of  the  lower  half  of  the  stone  in  water 
had  a  remarkable  effect  on  the  results. 

The  pressure  can  be  increased  enormously  with  a  corre- 
sponding greater  efficiency  in  the  work  of  the  stone,  although 


MECHANICAL  WOOD  PULP 


103 


h*  <O  Uy/    _j  Xfc  **}  ^  ^t  ^* 

-sjnoft   tz  Jdd  d/ry  jo  '^M^  £  SAID  0;  p9jmo9J  'd'fj 

FIG.  15.—  Curve  for  illustrating  Power  Trials. 


104  WOOD  PULP  AND   ITS   USES 

the  power  required  does  not  vary  much.  This  is  shown  by 
the  curve  D,  which  after  a  pressure  of  about  8  Ibs.  to  the 
square  inch  assumes  a  horizontal  position. 

Kirchner  found  that  the  output  per  unit  of  area  of  the 
total  grinding  surface  was  almost  proportional  to  the 
pressure. 

The  diagram  in  Fig.  15  represents  the  results  of  some  of 
the  more  important  tests. 

Curve  A . — With  a  pressure  of  1 J  Ibs.  per  square  inch  a 
stone  with  fine  surface  required,  in  twenty-four  hours,  7J 
h.p.,  and  with  a  pressure  of  3  Ibs.  per  square  inch,  4Jh.p. 
The  greatest  production  was  obtained  when  the  pressure 
reached  4J  Ibs.  per  square  inch,  when  the  power  required 
to  treat  2  cwt.  of  wood  amounted  to  4  h.p. 

Curve  B. — This  curve  represents  the  work  of  an  average 
stone  which  required  3  h.p.  under  a  pressure  of  4J  Ibs. 
per  square  inch.  The  power  under  a  higher  pressure 
of  14  Ibs.  per  square  inch  was  only  2J  h.p.  for  the  same 
production. 

Curve  C  represents  the  work  of  a  coarse  stone,  the 
amount  of  power  for  a  given  production  being  reduced  by 
the  increase  of  pressure  down  to  a  certain  point,  after  which 
any  further  increase  of  pressure  required  a  greater  amount 
of  power.  This  is  shown  by  the  sudden  rise  of  the  curve 
when  the  pressure  reached  13  Ibs.  per  square  inch. 

Kirchner  in  his  interesting  experiments  pointed  out  that 
these  tests  show  the  relation  between  the  production  of 
pulp  with  different  kinds  of  stone  at  different  pressures,  and 
shows  that  for  a  maximum  output  under  economical  condi- 
tions it  is  important  to  choose  the  right  pressure  for  a 
given  stone.  In  a  further  series  of  experiments  he  kept 


MECHANICAL  WOOD  PULP 


105 


the   stone  partially   immersed  in  a  mixture  of  pulp  and 
water.     The  results  are  shown  in  curves  D  and  E. 

Curve  D. — With  a  pressure  of  4J  Ibs.  per  square  inch 
the  power  required  for  the  production  of  2  cwt.  of  pulp  per 
twenty-four  hours  was  5J  h.p.  The  gradual  increase  of 
pressure  was  accompanied  by  a  reduction  in  the  amount  of 


FIG.  16.— Shaking  Screen. 

power  required,  and  with  a  pressure  of  15  Ibs.  per  square  inch 
the  power  was  reduced  to  4  h.p.  The  practical  effect  of  the 
greatly  increased  pressure  was  seen  in  the  finer  condition 
of  the  pulp. 

Screening. — The  pulp  from  the  grinders  is  carefully 
screened  to  remove  all  chips  and  insufficiently  ground  pulp. 
Many  forms  of  apparatus  are  employed,  but  all  are  based 
upon  the  same  principle,  the  use  of  plates  perforated  with 


106 


WOOD  PULP  AND  ITS  USES 


fine  slits  or  circular  holes  allowing  all  the  finer  pulp  to  pass 
through,  but  retaining  all  coarse  pieces. 

The  shaking  screen  shown  in  Fig.  16  consists  of  a  horizontal 
shallow  tray  perforated  with  fine  slits.  The  pulp,  mixed 
with  large  quantities  of  water,  flows  on  to  the  tray,  which  is 


FIG.  17A.— Centrifugal  Screen  for  Wood  Pulp. 

kept  in  a  violent  state  of  agitation,  and  the  fine  pulp 
together  with  the  water  falls  through  the  slits,  while  the 
coarse  stuff  is  gradually  forced  along  the  surface  of  the 
tray  and  eventually  falls  over  the  edge  into  a  trough  of 
water  or  a  travelling  band  conveyor. 

A  fiat  screen  is  worked  on  a  somewhat  similar  principle, 
but  the  motion  of  the  plate  is  due  to  a  violent  agitation 


MECHANICAL  WOOD   PULP 


107 


produced  in  a  vertical  direction  instead  of  being  to  and  fro 
in  the  horizontal  direction.  This  produces  a  partial  suction. 
The  centrifugal  screen,  Fig.  I?A,  the  latest  form  of 
apparatus  for  separating  out  the  coarse  pulp,  is  a  round 
vessel,  containing  a  circular  screen  built  up  of  perforated 


-C— 


FIG.  17B.— Section  of  Centrifugal  Screen  for  Wood  Pulp. 


plates,  which  rotates  at  a  high  rate  of  speed,  the  fine  pulp 
being  forced  through  the  slits  by  centrifugal  force. 

The  capacity  of  a  screen  is  usually  expressed  in  terms  of 
the  weight  of  dry  pulp  obtained  in  a  given  period.  Such 
figures  are  not  of  much  value  without  details  as  to  the  size 
and  number  of  the  perforations  per  square  foot  of  area,  as 
the  capacity  is  readily  increased  by  the, simple  process  of 
enlarging  the  slits  or  holes. 


108  WOOD   PULP  AND   ITS  USES 

Removal  of  Water. — When  the  pulp  has  been  properly 
screened,  it  is  treated  in  a  wet  press  machine  in  order  to 
remove  the  large  quantity  of  water  with  which  it  is 
mixed,  and  to  produce  a  pulp  fit  for  shipment  to  the 
paper  mill. 

The  dilute  mixture  is  pumped  continuously  into  a  large 
vat  in  which  rotates  a  hollow  drum  the  surface  of  which  is 
made  of  fine  wire  gauze.  The  pulp  adheres  to  the  drum, 
while  the  water  is  forced  through  the  wire  cloth  and  flows 
away  into  a  trough  fixed  outside  the  vat.  The  thin  skin  of 
pulp  is  carried  up  above  the  surface  of  the  water  in  the  vat 
and  is  picked  off  by  a  travelling  felt  passing  over  a  roller 
which  is  in  contact  with  the  drum.  The  thin  sheet  passes 
between  small  rollers,  which  squeeze  out  more  water,  and  is 
then  wound  up  in  a  continuous  roll  on  a  large  wooden  drum 
until  it  forms  a  thick  sheet.  This  is  removed  at  intervals 
either  by  hand  or  automatically. 

In  the  most  approved  form  of  wet  press  machine  the 
thick  sheet  is  cut  off  at  regular  intervals  by  a  knife  which 
falls  automatically.  The  sheet  of  pulp  is  therefore  always 
of  uniform  thickness  and  weight,  provided  reasonable  care 
has  been  exercised  in  keeping  the  ratio  of  water  and  pulp 
fairly  constant.  From  the  wet  press  machine  the  pulp  is 
obtained  in  the  form  of  thick  sheets  containing  about  75  per 
cent,  of  water. 

The  sheets  of  pulp  are  finally  submitted  to  pressure  in 
powerful  hydraulic  presses  which  remove  a  further  quantity 
of  water  and  give  a  product  containing  50  per  cent,  of  air- 
dry  pulp  and  50  per  cent,  of  water.  These  sheets  are 
packed  in  bales  of  4  cwt.  and  2  cwt.  capacity,  and  then 
fastened  up  with  stout  iron  wire  and  wooden  battens. 


MECHANICAL  WOOD  PULP  109 

BROWN  WOOD  PULP. 

In  1862  Lyman  patented  a  process  for  submitting  wood 
to  the  action  of  water  at  a  high  temperature,  160°  C.  In 
1870  Meyh  found  that  when  wood  previously  digested  in 
this  way  was  mechanically  treated  in  the  grinder  it  gave  a 
tough  long-fibred  stock.  Since  that  date  large  quantities 
of  brown  wood  pulp  have  been  produced  for  the  manufacture 
of  box  boards.  The  wood  is  either  simply  steamed,  in 
which  case  a  dark  brown  product  is  obtained,  or  digested  in 
water  at  high  pressure  when  a  lighter  coloured  paper  is 
produced. 

Steamed  Wood. — Logs  of  wood  12  or  16  feet  long,  or  cut 
up  in  2  feet  lengths  ready  for  the  grinder,  are  packed  into 
tall  cylindrical  boilers  and  steamed  for  twelve  to  thirty 
hours  at  a  temperature  varying  from  120°  to  160°  C.,  the 
shorter  period  requiring  a  higher  pressure.  The  water  of  con- 
densation containing  organic  acids  and  volatile  compounds 
such  as  acetic  and  formic  acids,  ethereal  oils,  turpentine 
and  resin  is  drawn  off  continuously,  or  at  intervals.  In 
modern  practice  such  by-products  are  carefully  preserved 
and  refined,  having  considerable  value. 

Wood  Digested  in  Water. — A  finer  material  of  superior 
colour  is  produced  when  the  wood  is  digested  for  twenty-four 
to  thirty  hours  at  a  somewhat  lower  temperature  in  the 
presence  of  water,  60  Ibs.  pressure  being  the  general 
practice. 

The  boilers  are  usually  cylindrical  in  shape,  and  of 
considerable  length,  erected  in  a  horizontal  or  vertical 
position.  Cast  iron  is  regarded  as  more  suitable,  being 
less  liable  to  oxidation  and  corrosion  from  the  organic 


FIG.  18. — Digestor  for  manufacture  of  Brown  Pulp. 


MECHANICAL   WOOD  PULP  111 

acids  produced  during  the  operation.  In  Germany  the 
practice  obtains  of  lining  the  vessels  with  copper,  and  in 
one  or  two  special  cases  digesters  made  of  copper  entirely 
have  been  built.  The  price  of  a  wrought-iron  copper-lined 
digestor  5  feet  diameter  and  17  leet  long  is  about  ^£192,  while 
a  digestor  constructed  entirely  of  copper  of  about  the  same 
capacity  would  cost  ^450. 

Use  of  Brown  Pulp. — Wood  boiled  in  this  way  previous 
to  grinding  gives  a  material  suitable  for  the  manufacture 
of  so-called  "  leather  board  "  used  for  box  making.  It  is 
exceedingly  tough  and  flexible,  can  be  bent  to  almost 
any  shape  without  cracking  or  splitting,  and  when  made 
up  into  boxes  is  capable  of  resisting  great  pressure.  It  is 
also  used  for  the  manufacture  of  imitation  kraft  paper 
and  for  common  paper  pattern  tissues. 

THE  ESTIMATION  OF  MECHANICAL  WOOD  PULP  IN  PAPERS. 

The  determination  of  the  exact  percentage  of  mechanical 
wood  pulp  in  papers  is  obviously  a  matter  of  importance. 
Considerable  attention  has  been  given  to  this  subject  of 
recent  years,  and  the  various  available  methods  may  be 
briefly  summarised. 

The  use  of  the  microscope  as  applied  to  the  detection 
and  estimation  of  different  fibres  in  a  sheet  of  paper  has 
long  been  known.  The  first  systematic  application  of 
quantitative  methods  to  the  vegetable  fibres  and  manu- 
factured products  is  that  of  Vetillart,  embodied  in  his 
treatise  "Etudes  sur  les  fibres  vegetales  textiles." 
Gottstein,  in  1884,  we  believe,  first  suggested  the  quanti- 
tative microscopic  method  of  counting  the  number  of 


112  WOOD   PULP  AND  ITS  USES 

mechanical  wood  fibres  in  a  given  field  of  a  specimen  care- 
fully mounted  using  as  a  test  for  comparison  specially 
prepared  papers  containing  known  percentages  of  mechani- 
cal pulp. 

Microscopic  Analysis. — The  paper  is  broken  up  into  pulp 
by  preliminary  treatment  with  a  weak  solution  of  caustic 
soda,  which  is  then  thoroughly  removed  by  means  of  hot 
water,  and  a  number  of  slides  are  mounted  for  inspection, 
Herzberg's  staining  reagent  being  used  to  colour  the  mass 
of  fibres.  Several  slides  are  so  prepared  and  carefully 
examined.  The  examination  is  best  effected  by  bringing 
every  portion  of  the  slide  into  the  field  of  view  of  the 
microscope,  a  record  being  made  for  each  field  of  view 
as  to  the  approximate  proportion  in  which  the  fibres  are 
present.  This  method  is  preferable  to  that  frequently 
employed,  of  absolutely  counting  the  fibres,  but  it  demands 
a  good  deal  of  previous  experience  with  pulp  mixtures  in 
which  the  proportions  are  already  known. 

The  usual  staining  reagents  which  may  be  used  for 
differentiating  fibres  examined  under  the  microscope  are 
various  aniline  dyes,  iodine  solutions  and  iodine  combined 
with  dehydrating  agents.  The  most  useful  reagent  for 
general  work  is  Herzberg's  iodine  and  zinc  chloride  solution. 
The  formulae  for  the  preparation  of  these  reagents  are  as 
follows : — 

Winkler— 
Potassium  iodide      ...         .5  grammes. 

Iodine 1  gramme. 

Water 20  c.c. 

Glycerine 1     ,, 


MECHANICAL  WOOD   PULP 


113 


Herzberg — 

Chloride  of  zinc     .         .         .         .20  grammes. 
Potassium  iodide   .         .         .         .21         „ 

Iodine O'l  gramme 

Water 5  grammes. 

The  colorations  produced  by  these  reagents  are  shown  in 
the  appended  table,  but  the  colour  reaction  varies  with  the 
purity  of  the  fibre,  and  the  percentage  of  moisture  present 
in  the  small  quantity  placed  on  the  microscope  glass. 

MICRO- CHEMICAL  EEACTIONS  OF  FIBRES. 


Fibres. 

Coloration  produced. 

Iodine  solution. 

Zinc  chloride, 
iodine  solution. 

Magnesium 
chloride, 
iodine  solution. 

Cotton,  linen,  hemp 

Brown 

Wine  -red 

Eeddish  brown 

Esparto,        straw, 

Grey  to  grey- 

Blue to  violet, 

Bluish  violet 

bamboo,  celluloses 

ish  brown. 

or    blue    to 

greyish  vio- 

let 

Wood  celluloses    . 

Colourless. 

Blue  to  bluish 

Light  brown 

violet 

to  red 

Manila  hemp 

Grey,  brown, 

Dark    yellow 

Yellow,  green- 

or yellowish 

or    greenish 

ish  yellow 

brown. 

yellow 

Mechanical     wood 

pulp,  jute    . 
Unbleached     Ma- 

Yellow. 

Yellow 

Yellow 

nila,    straw  (par- 

tially boiled) 

Yellow. 

Yellow. 

Yellow 

Colour  Methods  of  Analysis. — Various  simple  colour 
reactions  are  known,  all  of  which  afford  a  rough  indication 
of  the  proportion  of  mechanical  wood  pulp  in  papers.  In 
1882,  Gaedicke  proposed  the  manufacture  of  a  series  of 
standard  papers  containing  varying  proportions  of 
mechanical  wood,  the  first  faper  in  the  series  to  consist 

w.p.  i 


114  WOOD  PULP  AND  ITS  USES 

of  pure  sulphite,  and  the  last  paper  of  the  series  containing 
95  or  100  per  cent,  of  mechanical  wood  pulp.  On  each  of 
the  standand  papers  a  solution  of  aniline  sulphate  of  known 
strength  produced  a  yellow  coloration,  the  intensity  of 
which  was  in  direct  proportion  to  the  amount  of  mechanical 
wood  pulp.  Equal  coloration  on  the  standard,  and  an 
unknown  paper  could  then  be  recorded  as  evidence  of  equal 
amounts  of  mechanical  wood  pulp,  and  this  reaction  would 
furnish  a  means  for  measuring  the  percentage  of  ground 
wood  pulp  in  the  paper.  The  following  reagents  can  be 
employed  for  this  purpose. 

Aniline  Sulphate.  —  4  grammes  of  the  salt  dissolved  in 
100  c.c.  of  water.  This  reagent  gives  a  yellow  colora- 
tion when  placed  on  paper  containing  mechanical  wood 
pulp. 

Phloroglucinol. — 2  grammes  of  phloroglucinol  are  dissolved 
in  100  c.c.  alcohol  and  50  c.c.  concentrated  hydrochloric 
acid  added.  The  solution  should  be  kept  in  the  dark. 
Gives  a  pink  to  crimson  coloration  more  or  less  intense 
according  to  the  proportion  of  mechanical  wood  present. 

Ferric  Ferricyanide. — Dissolve  1*6  grammes  ferric  chloride 
in  100  c.c.  of  water.  Dissolve  3'3  grammes  potassium 
ferricyanide  in  100  c.c.  of  water.  Equal  quantities  of  the 
solutions  to  be  mixed  and  used  only  when  required.  Gives 
a  Prussian  blue  colour  with  mechanical  wood  pulp. 

Wurster's  Reagent. — 2  grammes  of  dimethyl  para- 
phenylenediamine  dissolved  in  100  c.c.  of  water.  Gives  a 
deep  red  colour  with  mechanical  wood  pulp  and  other 
lignified  fibres. 

Phenol. — A  dilute  solution  of  phenol  gives  a  greenish 
blue  colour  with  mechanical  wood  pulp. 


MECHANICAL  WOOD  PULP  115 

Chemical  Methods  of  Analysis. — Biiller  in  1887  suggested 
a  method  based  on  the  solubility  of  cellulose  in  ammoniacal 
copper  oxide.  The  paper,  having  been  suitably  broken  up 
into  pulp,  is  treated  with  the  solution,  and  the  cellulose 
dissolves  fairly  quickly,  leaving  the  mechanical  wood  pulp 
as  an  insoluble  residue  to  be  filtered,  washed,  dried,  and 
then  weighed.  The  cellulose  estimations  obtained  by  this 
process  are  not  very  satisfactory. 

The  reaction  of  the  ligno-celluloses  with  iodine  has  also 
been  suggested  as  the  basis  of  a  method  of  quantitative 
analysis.  The  paper  reduced  to  the  condition  of  pulp  is 
allowed  to  remain  in  contact  with  a  definite  quantity  of 
iodine  dissolved  in  potassium  iodide.  After  standing  twenty- 
four  hours  the  amount  of  iodine  left  in  the  solution  is 
determined  by  titration  with  sodium  thiosulphate,  the 
amount  of  iodine  absorbed  being  a  measure  of  the  amount 
of  mechanical  pulp  present. 

Godeffroy  and  Coulon  proposed  a  method  dependent  upon 
the  reaction  between  lignified  wood  fibre  and  chloride  of 
gold.  The  paper  is  torn  up  into  fine  shreds,  divided  into 
two  equal  portions  of  convenient  weight,  and  boiled  for 
about  ten  minutes  in  a  10  per  cent,  solution  of  aqueous 
ammonia,  then  thoroughly  washed  and  dried.  One  portion 
is  burnt  for  the  determination  of  ash.  The  second  portion 
is  extracted  with  a  hot  alcoholic  solution  of  tartaric  acid, 
dried,  and  then  successively  extracted  with  alcohol  and 
ether.  The  residue  left  is  then  boiled  for  about  fifteen 
minutes  with  a  dilute  solution  of  gold  chloride,  the  latter 
filtered  and  removed  by  washing.  The  dried  fibre  containing 
the  adherent  reduced  gold  is  then  burnt  and  the  weight  of 
ash  and  gold  ascertained.  The  difference  between  the  ash 

i  2 


116  WOOD   PULP  AND  ITS  USES 

previously  weighed  and  the  weight  of  ash  and  gold 
together,  measures  the  quantity  of  gold  reduced  to  a 
metallic  state,  and  the  latter  is  an  indication  of  the 
proportion  of  lignified  fibre  in  the  sample  of  paper. 
Numerous  experiments  conducted  by  Godeffroy  and  Coulon 
show  that  under  these  conditions  100  parts  of  mechanical 
wood  pulp  per  se  will  reduce  21'2  parts  of  gold. 

Benedikt  proposed  a  method  based  upon  the  reaction 
between  lignified  fibre  and  hydriodic  acid,  the  products  of 
decomposition  being  added  to  silver  nitrate,  with  the 
precipitation  of  silver  iodide.  The  weight  of  dry  silver 
iodide  is  taken  as  a  measure  of  the  mechanical  wood  pulp 
present. 

The  action  of  chlorine  gas  on  ligno-cellulose  is  also 
suggested  as  the  basis  of  a  quantitative  method  of  analysis 
for  mechanical  wood  pulp.  The  paper  is  boiled  in  a  weak 
solution  of  carbonate  of  soda,  washed  thoroughly  with  weak 
acetic  acid,  and  then  with  hot  water  until  quite  neutral. 
The  paper  is  pressed  and  exposed  in  a  damp  condition  to 
the  action  of  pure  washed  chlorine  gas.  After  complete 
chlorination  the  excess  of  chlorine  gas  is  blown  out  of  the 
vessel,  and  a  known  volume  of  water  added  to  the  bleached 
pulp.  The  quantity  of  hydrochloric  acid  in  the  aqueous 
solution  is  determined  by  titration  with  standard  soda 
solution. 

The  acid  equivalent  to  one  gramme  of  various  pulps  is  as 
follows : — 

Mechanical  wood  pulp      .     4*4    c.c.  normal  alkali 
Aspen  mechanical  pulp     .     3'5    c.c.       ,,  ,, 

Unbleached  sulphite         .     0*46  c.c.       ,,          ,, 
Bleached  sulphite  .     0'03  c.c.       „          ,, 


MECHANICAL  WOOD   PULP  117 

The  most  recent  method  devised,  by  Cross  and  Bevan 
is  based  upon  the  well-known  phloroglucinol  reaction.  A 
weighed  quantity  of  the  paper  previously  broken  into  pulp 
is  placed  in  a  solution  of  standard  phloroglucinol,  the  strength 
of  which  has  been  previously  found.  The  quantity  of 
phloroglucinol  in  solution  before  and  after  immersion  of  the 
fibre  is  determined  by  titration  with  formaldehyde.  It  has 
been  shown  that  all  lignified  fibres  possess  what  may  be  called 
a  constant  "  phloroglucinol  absorption  value." 

The  details  of  the  process  are  as  follows  :  — 

Two  grammes  of  the  material  are  dried  at  100°  0. 
and  then  weighed.  The  weighed  amount  is  transferred  to 
a  dry  flask,  covered  with  40  c.c.  of  phloroglucinol  solution 
(made  by  dissolving  2'5  grammes  of  pure  phloroglucinol  in 
500  c.c.  of  hydrochloric  acid  of  1*06  sp.  gr.),  shaken  and 
allowed  to  stand  for  some  hours,  preferably  all  night.  The 
liquid  is  then  filtered  through  cotton-wool  placed  in  the 
neck  of  a  funnel.  The  filtrate  is  next  titrated,  10  c.c.  being 
mixed  with  20  c.c.  of  hydrochloric  acid  of  1*06  sp.  gr.  and 
heated  to  70°  C.  Standard  formaldehyde  solution  (made 
by  dissolving  1  c.c.  of  40  per  cent,  formaldehyde  in 
500  c.c.  of  hydrochloric  acid  of  1'06  sp.  gr.)  is  now  added, 
1  c.c.  at  a  time,  two  minutes  being  allowed  to  elapse  between 
each  addition. 

As  indicator  of  the  presence  of  phloroglucinol,  a  piece  of 
cheap  newspaper  is  used.  A  red  stain  is  produced  in  the 
presence  of  free  phloroglucinol  when  a  drop  of  the  liquid 
is  allowed  to  fall  on  the  paper. 

Towards  the  end  of  the  titration  the  stain  gradually 
takes  longer  and  longer  to  appear  on  the  paper,  and  finally 
it  is  necessary  to  carefully  dry  the  paper  before  a  Bunsen 


118  WOOD  PULP  AND  ITS  USES 

flame.  The  end  of  the  filtration  is  indicated  when  the 
stain  is  no  longer  perceptible. 

10  c.c.  of  the  original  phloroglucinol  solution  are  then 
titrated  under  exactly  the  same  conditions,  the  amount  ab- 
sorbed by  the  ligno-cellulose  being  obtained  by  the  difference 
between  the  two  figures.  This  phloroglucinol  absorption 
value  is  expressed  as  a  percentage  on  the  dry  weight  of  the 
ligno-cellulose. 

The  following  values  have  been  obtained :  Wood  flour, 
7'9 ;  mechanical  wood,  6'71 ;  jute  (best  quality),  3'98  ;  jute 
(average  quality),  4*26 ;  sulphite  wood  pulp,  0*75  ;  and 
cotton,  0*2  per  cent,  of  phloroglucinol. 

For  the  calculation  of  the  mechanical  wood  in  paper  the 
following  formula  is  used,  8*0  being  the  absorption  value 
for  mechanical  wood,  and  1/0  that  of  sulphite  pulp,  p  the 
absorption  value  of  the  dry  ash -free  sample,  and  H  the 
percentage  of  mechanical  wood  in  the  paper. 

H       100  (p-  1-0) 
8-0  -  1-0 

Sources  of  error,  and  the  conditions  necessary  for  the 
most  constant  and  accurate  results  are  : — 

1.  The  purity  of  the  phloroglucinol  used.     The  standard 
solution  is  made  from  a  weighed  amount  of  this  substance. 
It  is  therefore  necessary  to  ensure  its  purity. 

2.  The  absorption  value  is  influenced  by  the  concentration 
of  the  phloroglucinol  solution.    The  quantities  to  be  used  are 
2  grammes  of  paper  and  40  c.c.  of  phloroglucinol  solution. 

3.  Generally,  it  is  unnecessary  to  remove  sizing  material 
from  the  paper   before   the  determination.     In   the  case, 
however,  of  large  quantities  being  present,  its  extraction 


MECHANICAL  WOOD  PULP 


119 


(by  warming  with  a  mixture  of  alcohol  and  ether)  is  to  be 
recommended,  the  reaction  taking  place  more  rapidly. 


EXAMPLES. 


Newspaper. 

Ash. 
Per  cent. 

Sizing. 
Per  cent. 

Phloroglucinol 
absorption. 
Per  cent. 

Mechanical 
wood. 
Per  cent. 

Times     . 

8'4 

1-5 

2-14 

16-3 

Daily  Telegraph 

2-4 

1-5 

2-40 

20-0 

Tribune  . 

10-2 

1-5 

5-23 

60-4 

Daily  Graphic 

15-1 

1-5 

5-0 

57-1 

\d.  paper  (white)    . 

1-5 

1-5 

6-62 

80-3 

\d,  paper  (pink) 

2-0 

1-5 

6-32 

76-0 

CHAPTEE  V 


CHEMICAL     WOOD     PULP 

THE  term  "  chemical,"  in  contradistinction  to  the  term 
"  mechanical,"  is  applied  to  wood  pulp  prepared  by  a 
chemical  process  in  which  the  isolation  of  the  fibre  is 
effected  by  treatment  of  the  wood  with  suitable  solutions. 
The  resultant  product  is  a  more  or  less  pure  form  of  cellu- 
lose, differing  very  materially  from  the  fibre  of  the 
mechanical  process.  In  the  latter  case  the  pulp  consists  of 
the  raw  wood  in  which  the  constituents  are  unchanged 
except  in  form  and  shape,  whereas  the  chemical  pulp 
is  entirely  different  in  composition  from  the  original 
material.  This  is  shown  in  an  analysis  given  by  Griffin 
and  Little  : — 


Spruce  wood. 

Spruce  cellules^. 

Moisture 

11-5 

6-7 

Ash 

0-3 

0-5 

Cellulose 

53-0 

89-7 

Lignin,  etc. 

35-2 

3-1 

100-0 

100-0 

The  methods  employed  for  the  preparation  of  cellulose 


CHEMICAL  WOOD  PULP  121 

from  wood  are  of  two  kinds,  namely,  the  acid,  of  which  the 
so-called  sulphite  process  is  typical,  and  the  alkaline, 
exemplified  by  the  well-known  soda  process. 

Preparation  oj  Wood. — Whichever  system  is  used  the 
preliminary  operations  for  preparing  the  wood  are  the  same. 
The  logs  are  cut  into  lengths  of  two  feet,  the  bark  com- 
pletely removed  by  the  methods  described  in  the  chapter  on 
Mechanical  Wood  Pulp,  and  subsequently  cut  up  into  small 
chips  by  special  machinery. 

For  the  best  qualities  of  pulp  the  knots  in  the  wood 
are  cut  out,  or  as  an  alternative  the  chips  of  wood  are 
carried  by  means  of  a  travelling  band  into  a  sorting  room 
and  all  the  knots  and  faulty  pieces  of  wood  removed  by 
hand. 

Sulphite  Process. — In  general  terms  this  consists  in  sub- 
mitting the  wood  to  the  action  of  sulphurous  acid  and  its  acid 
salts  in  closed  vessels  at  high  pressure  for  definite  periods 
of  time.  The  quality  of  the  product  can  be  varied  to  almost 
any  extent  by  the  conditions  of  treatment,  that  is  by  varying 
the  strength  of  liquor,  the  steam  pressure,  and  the  period 
of  time  occupied  in  digestion.  This  may  be  shown  by  a 
study  of  the  several  qualities  of  sulphite  pulp  available  for 
paper-making. 

Quick  Cook  Process. — This  term  is  applied  to  pulp 
prepared  by  digesting  the  wood  at  a  high  pressure  of  80 — 
100  Ibs.  per  square  inch  for  a  period  of  eight  to  nine 
hours.  If  the  operation  is  carried  out  to  an  extreme  limit, 
using  the  strong  liquor,  a  soft  pulp  is  obtained  of  good 
colour  which  bleaches  very  rapidly  with  a  small  proportion 
of  bleaching  powder.  If  on  the  other  hand  the  treatment  is 
carried  out  with  a  minimum  quantity  of  liquor  just  sufficient 


122  WOOD  PULP  AND   ITS  USES 

to  produce  complete  disintegration  of  the  wood,  then  the 
pulp  obtained  is  of  a  reddish  colour,  not  easily  bleached, 
but  which  is  characterised  by  great  strength  and  toughness. 
The  latter  kind  of  pulp  is  eminently  suited  for  the  manu- 
facture of  news  and  wrapping  papers,  in  which  strength 
is  of  primary  importance,  whereas  the  former  quality  of 
pulp  produced  by  excessive  boiling  is  more  suitable  for 
book  papers  and  writings  in  which  colour  is  of  greater 
importance. 

Slow  Cook  Process. — This  method  differs  radically  from 
the  quick  process,  in  that  the  pressure  is  seldom  allowed  to 
exceed  15  Ibs.,  while  the  time  of  boiling  occupies  thirty  to 
forty-eight  hours.  Moreover,  the  heat  is  applied  by  means 
of  steam  passed  through  lead  coils  so  that  the  condensed 
steam  produced  does  not  accumulate  in  the  digestor  itself. 
The  pulp  obtained  in  this  case  is  of  excellent  quality  and  of 
great  strength,  being  particularly  adapted  for  the  produc- 
tion of  papers  such  as  imitation  parchments.  It  is  frequently 
described  as  "  Mitscherlich  "  pulp  from  the  name  of  the 
inventor  of  the  process. 

Sulphite  Liquor. — The  chemical  solvent  used  in  the 
bi-sulphite  process  is  a  solution  of  bi-sulphite  of  lime  con- 
taining a  certain  proportion  of  free  sulphurous  acid.  It  is 
prepared  by  burning  sulphur  or  pyrites  rich  in  sulphur,  in 
suitable  ovens,  and  passing  the  sulphurous  acid  gas  obtained 
through  tanks  containing  milk  of  lime,  or  through  towers 
containing  blocks  of  limestone  moistened  with  water. 
Many  different  systems  are  in  use  for  burning  the  sulphur 
under  regulated  conditions,  and  for  producing  a  liquid 
containing  definite  proportions  of  lime  or  magnesia 
sulphites  and  free  sulphurous  acids.  The  proportions 


~ 


CHEMICAL  WOOD  PULP  123 

vary   in   different    mills,    the    following   being  typical   of 
many  :  — 

Free  sulphurous  acid    .         .         .     2*03  per  cent. 
Combined  sulphurous  acid    .         .     1*01       „ 
Lime     ......     0'83 

The  quantity  of  sulphur  required  per  ton  of  finished  pulp 
varies  from  250  Ibs.  to  400  Ibs.  Considerable  attention  is 
now  given  to  methods  by  means  of  which  the  sulphurous 
acid  gas  which  comes  away  from  the  digestors  during  the 
operation  is  utilised,  thereby  reducing  the  amount  of 
sulphur  actually  required  per  ton. 

Waste  Sulphite  Liquors.  —  The  waste  liquors  discharged 
from  the  boilers  when  the  wood  has  been  boiled  are  at 
present  thrown  away.  Many  attempts  have  been  made  to 
recover  the  by-products,  but  no  system  has  yet  been  intro- 
duced for  the  recovery  of  the  sulphur  on  a  large  commercial 
scale  likely  to  be  remunerative,  or  for  the  manufacture  of 
by-products  having  any  practical  value. 

The  problem  has  long  been  a  serious  one,  for  in  1894  a 
prize  of  10,000  marks  was  offered  in  Germany  for  a  prac- 
ticable method  of  preventing  the  pollution  of  streams  by 
the  waste  liquor  of  sulphite  mills,  but  no  serviceable  process 
has  been  devised.  The  volume  of  liquor  is  so  large,  that 
the  difficulties  are  greatly  increased.  One  ton  of  air-dry 
pulp  gives  about  2,500  gallons  of  acid  liquor  which  diluted 
with  a  sufficient  quantity  of  wash  waters  required  for 
cleaning  the  pulp  blown  from  the  digestors  is  increased  to 
about  10,000  to  12,000  gallons. 

Hoffmann*  gives  the  analyses  of  several  waste  liquors  as 
follows  :  — 
*  Hoffmann,  C.,PractischesHandbuch  der  Papier  Fabrikation,  1897. 


124  WOOD  PULP  AND  ITS 

ANALYSES  OF  SULPHITE  PULP  WASTE  LIQUOR. 


Grammes  per  litre. 

1 

2 

3 

4 

5 

Total  solids. 

82-0 

88-0 

85-0 

93-0 

92-0 

Loss  on  ignition  . 

68-0 

75-0 

69-0 

81-0 

— 

Ash     .... 

14-0 

13-0 

16-0 

12-0 

— 

Total  sulphur 

— 

— 

— 

— 

9-2 

Free   sulphur  dioxide 

(S02)      .        .        . 

2-6 

2-2 

2-9 

2-6 

3-8 

Sulphite  radicle  (SOS)  . 

7-3 

7-9 

6-7 

1-2 

3-8 

Sulphate  radicle  (S04) 

4-1 

5-4 

4-8 

2-7 

1-9 

Oxygen  consumed 

52-0 

52-0 

50-0 

60-0 

— 

The  characteristic  constituent  of  these  liquors  is1  the 
lignone-sulphonic  acid  (calcium  salt)  resulting  from  the 
specific  interaction  of  the  bi-sulphites  with  the  aldehydic  or 
quinonic  complex  of  the  wood  or  ligno-cellulose. 

The  free  lignone-sulphonic  acid  gives  a  characteristic 
reaction  with  gelatin,  precipitating  a  colloidal  viscous 
mass,  which  may  be  re-dissolved  in  weak  alkaline  liquids, 
and  when  so  re-dissolved  has  been  employed  in  engine- 
sizing  papers.  The  reaction  with  gelatin  suggests  its 
employment  as  a  "  tanning  "  agent  in  the  manufacture  of 

1  Lindsay  and  Tollens,  Annalen,  267—341 ;  H.  Seidel,  Zeitschr. 
Angew.  Chem.,  1900;  Suringar  Diss.  Gottingen,  1892;  Klason. 
Chem.  Ztg.,  1897,  261 ;  Seidel  und  Hanak.  Mitt.  Techn.  Gew.  Mus. 

1897—8. 


CHEMICAL  WOOD   PULP  125 

leathers ;  and  a  certain  amount  of  the  liquor  is  being  utilised 
in  this  industry. 

In  addition  to  the  characteristic  lignone-sulphonic  acid, 
and  excess  of  sulphurous  acid,  free  and  combined,  the 
liquors  contain  a  certain  proportion  of  carbohydrates; 
and  hence  after  treatment  of  the  liquors  to  bring  about 
the  necessary  conditions,  a  process  of  fermentation  is 
induced  by  the  introduction  of  yeast,  from  which  alcohol 
results. 

The  subject  of  the  composition  and  utilisation  of  sulphite 
liquors  has,  in  fact,  been  extensively  studied,  and  the 
following  brief  account  of  the  processes  patented  during  the 
last  thirty  years  may  be  added.  Cross  and  Bevan  observed 
the  reaction  of  the  lignone  sulphonates  and  patented  the 
production  of  the  insoluble  colloidal  compound  and  its  use 
in  the  engine-sizing  of  papers.  [E.  P.  1548,  1883.] 

Mitscherlich  revived  the  method  of  mixing  gelatine  or 
some  cheaper  form  of  animal  size  with  the  spent  lye,  in 
order  to  obtain  a  tannin  size  suitable  for  sizing  paper  in 
the  beating  engine.  By  using  ordinary  rosin  size  in  con- 
junction with  the  new  product  he  claimed  a  reduction  in  the 
cost.  [D.  E.  P.  93,944—5.] 

Ekman  obtained  a  substance  which  he  called  "  Dextron  " 
by  concentrating  the  liquors  to  34°  Be.  and  adding  magne- 
sium sulphate.  The  product  was  applied  to  the  dressing  of 
textile  fabrics  to  render  them  partially  waterproof  and  to 
secure  them  from  mildew.  [D.  R.  P.  81,643.] 

Dr.  Frank  proposed  the  addition  of  milk  of  lime  to  the 
waste  liquor  so  as  to  separate  the  sulphites  as  calcium 
sulphite,  the  remaining  liquid  to  be  discharged  as  com- 
paratively harmless. 


126  WOOD  PULP  AND   ITS  USES 

The  presence  of  the  large  proportion  of  organic  matter  in 
the  liquor  has  suggested  the  basis  of  a  scheme  for  the 
manufacture  of  compressed  fuel.  Attempts  have  been 
made  to  concentrate  the  waste  liquors  to  a  syrupy  con- 
sistency and  to  employ  this  paste  in  conjunction  with 
sawdust,  coal  dust  or  charcoal  for  the  production  of 
briquettes. 

Dorenfeldt  patented  a  modification  of  the  ordinary  calcium 
bi-aulphite  process  which  appeared  to  make  the  subsequent 
treatment  of  the  spent  digestor  lyes  a  more  profitable 
undertaking.  Sulphate  of  soda  was  added  to  the  usual 
bi-sulphite  of  lime  liquor,  whereby  a  precipitate  of  sulphate 
of  lime  was  obtained,  and  a  solution  of  bi-sulphite  of  soda. 
The  sulphate  of  lime  was  filtered  off  and  sold  as  "  pearl 
hardening"  for  the  loading  of  paper,  and  the  bisulphite  of 
soda  used  for  digesting  wood.  The  soda  was  recovered  by 
concentration  and  incineration  and  afterwards  converted 
into  caustic  soda  by  the  ordinary  methods. 

Drewson  proposed  to  heat  the  stronger  waste  liquors 
with  lime  under  pressure,  the  resultant  product  calcium 
mono-sulphite  being  subsequently  converted  into  the  soluble 
bi-sulphite  with  sulphurous  acid  gas.  The  cost  of  the 
process  and  the  impurity  of  the  regenerated  liquor  are 
conditions  which  have  prevented  the  development  of  a 
likely  scheme  for  recovery.  [D.  R.  P.  67,889.] 

Destructive  distillation  has  been  experimentally  tried, 
but  the  yield  of  useful  products  is  much  too  low.  The 
formation  of  oxalic  acid  by  fusion  of  the  concentrated  liquor 
with  alkali  has  also  been  proved,  but  the  quantity  obtained 
was  too  small  to  render  any  operations  on  a  large  scale 
commercially  possible. 


CHEMICAL  WOOD  PULP  127 

"  Lignorosin,"  a  substance  obtained  by  converting  the 
lignone-sulphonic  acid  into  a  soda  salt,  has  been  success- 
fully applied  in  mordanting  woollen  goods.  Its  use  in  this 
direction  is  naturally  very  limited,  and  offers  no  induce- 
ment to  manufacture  on  a  large  scale. 

The  utilisation  of  the  lignone-sulphonates  by  treatment 
with  nitric  acid  for  the  manufacture  of  colouring  matters  is 
suggested  by  the  reactions  of  the  lignone  constituents  of 
wood  with  nitric  oxides.  The  treatment  of  these  substances 
with  nitric  acid  gives  a  series  of  orange  and  yellow  dyes 
which  produce  bright  shades  on  wool  and  silk.  Fusion  of 
"lignone"  with  sodium  sulphide  and  crude  sulphur  gives 
a  sulphur  dye  that  colours  cotton  dark  green,  changing  to 
black  in  a  chrome  bath.1 

The  manufacture  of  a  tanning  substitute  involves  a 
certain  purification  of  the  waste  sulphite  liquor  to  eliminate 
the  excess  of  mineral  sulphites,  and  a  certain  proportion  of 
soluble  iron  compounds,  which  produce  discoloration  when 
used  in  association  with  ordinary  tanning.  Considerable 
activity  is  being  shown  in  this  direction,  with  some  prospect 
of  success. 

Kobeson  has  patented  a  process  for  tanning  skins  and 
hides  in  which  a  liquor  containing  a  compound  of  sesqui- 
oxide  of  aluminium  or  some  other  base  with  the  practically 
unchanged  organic  matter  of  waste  sulphite  liquors  is 
employed.  The  lye  is  treated  with  the  sesqui-oxide  in 
conjunction  witli  an  acid  capable  of  precipitating  mineral 
matter  from  the  liquor. 

As  25  per  cent,  of  the  solid  residue  in  sulphite  liquors 

1  Pollution  of  Streams  by  Sulphite  Pulp  Waste.  E.  B.  Phelps, 
U.S.A.  Geological  Survey  Dept.  » 


128  WOOD  PULP  AND   ITS   USES 

can  be  removed  from  solution  by  the  hide  powder  test,  the 
process  seems  promising. 

A  writer  in  the  Wochenblatt  has  suggested  the  incorpora- 
tion of  the  lyes  with  soap,  claiming  that  the  resinous  and 
glucose  substances  present  together  with  the  mineral  salt, 
would  produce  a  new  soap  of  good  lathering  and  cleansing 
properties. 

Knosel  suggests  a  process  for  mixing  the  sulphite  lye 
after  suitable  concentration  with  an  equal  weight  of  phos- 
phate of  lime,  thereby  obtaining  a  solid  and  soluble 
compound  to  be  used  as  a  fertiliser,  the  manurial  qualities 
of  the  phosphate  of  lime  being  increased  80  per  cent. 

Elb  adds  formaldehyde  to  the  sulphite  liquors  during 
concentration  and  obtains  an  adhesive  substance,  clear  and 
transparent,  soluble  in  water.  The  formaldehyde  is  said 
to  prevent  the  separation  of  salts  during  evaporation. 

Alcohol  from  Waste  Lye. — The  most  recent  and  interesting 
attempt  to  deal  with  the  waste  sulphite  liquors  is  seen  in 
the  experiments  now  being  carried  out  on  a  large  scale 
in  Sweden  for  the  production  of  alcohol.  The  process  is 
being  worked  on  a  fairly  large  scale  under  Ekstrom's 
patents  at  Skutskar  in  Sweden,  the  average  yield  of  alcohol 
being  60  litres  per  ton  of  cellulose,  no  less  than  54,000 
litres  having  been  produced  during  1909. 

In  1819,  Braconnet  observed  that,  by  the  action  of 
sulphuric  acid  on  wood,  grape  sugar  was  formed,  which 
could  be  fermented  to  yield  alcohol. 

In  1898,  Simonsen  obtained  60  litres  of  spirit  from  one 
ton  of  wood  by  this  acid  process. 

In    America.,    Ewen    and    Tomlinson,    acting    on    the 


CHEMICAL  WOOD  PULP  129 

suggestion  of  Classen,  obtained  78  litres  of  spirit  by  the 
action  of  sulphurous  acid  on  wood. 

In  1891,  Lindsay  and  Tollens  found  1/2  per  cent,  of  fer- 
mentable carbohydrates  in  the  dry  solids  of  waste  sulphite 
liquor,  and  obtained  about  60  litres  per  ton  of  cellulose. 

Two  processes  have  now  been  patented  in  which  the  lyes 
are  first  neutralised  by  carbonate  of  lime.  In  Wallin's 
method  ordinary  lime  is  used  for  neutralising  the  liquor, 
and  in  Ekstrom's  system  the  waste  lime  sludge  of  the 
sulphate  cellulose  mills  is  employed.  Schwalbe  states  that 
the  neutralisation  sludge  obtained,  after  the  process,  con- 
tains sufficient  calcium  sulphite  to  effect  a  saving  of  40  per 
cent,  of  the  sulphur  required  for  boiling  wood. 

The  volume  of  liquor  to  be  treated  amounts  to  10,000 
litres  for  every  100  tons  of  cellulose  and  the  dry  precipitate 
obtained  on  neutralising  amounts  to  15  tons.  The  liquid, 
after  being  neutralised,  is  cooled,  aerated,  then  fermented 
for  72  hours  at  a  temperature  of  75°  C.,  by  means  of  yeast, 
and  afterwards  distilled.  The  alcohol  obtained  contains 
considerable  proportions  of  methyl  alcohol,  aldehydes, 
furfural  and  acetone.  It  may  be  noted  that  this  process, 
while  interesting  as  showing  the  possibility  of  obtaining 
useful  products  from  the  waste  liquor,  does  not  deal  with 
the  serious  problem  of  the  prevention  of  pollution  of  streams 
by  the  discharge  of  the  waste  liquor. 

The  direct  recovery  of  the  original  sulphur  has  not  yet 
been  evolved  as  a  satisfactory  process.  Evaporation  and 
combustion  of  the  concentrated  lye  means  a  large  loss  of 
sulphur,  and  a  method  for  the  regeneration  of  the  latter 
from  organic  sulphur  compounds  has  yet  to  be  discovered. 
Obviously  this  is  the  correct  solution  of  a  difficult  problem, 

W.P.  K 


130  WOOD  PULP  AND  ITS  USES 

as  it  might  avoid  the  formation  of  a  large  quantity  of 
by-products  which  find  no  useful  application  in  paper- 
making  or  any  industrial  operations. 

Washing  and  Finishing. -—The  pulp  discharged  from  the 
digestor  is  thoroughly  washed  with  water  for  the  removal 
of  the  spent  liquor,  and  then  subjected  to  a  careful  screening 
in  order  to  remove  incompletely  digested  pieces  of  wood 
and  any  dirt  which  may  be  present. 

This  is  effected  by  screens  of  various  kinds,  all  based 
upon  the  same  principle,  though  differing  in  construction. 
The  apparatus  most  frequently  employed  is  the  flat  screen, 
consisting  of  a  heavy  cast-iron  shallow  tray  fitted  with  brass 
plates  which  contain  fine  slits.  The  tray  is  kept  in  a  state  of 
violent  agitation,  so  that  the  mixture  of  pulp  and  water 
flowing  into  the  tray  is  also  continuously  shaken.  By  this 
means  the  pulp  is  easily  screened,  the  pure  material  finding 
its  way  through  the  slits,  while  the  coarse  lesser-cooked 
material  remains  on  the  surface  of  the  screen. 

The  pulp  is  then  sorted  up  into  various  qualities,  the 
coarse  residue  being  sold  at  a  low  price  as  "  screenings." 

The  fibre  passing  through  the  screens,  being  mixed  with 
a  very  large  volume  of  water,  is  then  subjected  to  a  process 
whereby  the  water  is  removed,  and  the  pulp  obtained  in  the 
form  of  moist  sheets,  containing  about  50  per  cent,  of 
moisture. 

Sulphite  pulp  is  usually  prepared  for  export  in  the  form 
of  dry  sheets,  and  these  are  produced  by  treating  the  pulp 
in  a  somewhat  different  manner.  The  wet  mixture  is  con- 
verted into  dry  sheets  by  means  of  a  machine  which  closely 
resembles  an  ordinary  paper-making  machine — that  is,  the 


CHEMICAL  WOOD  PULP  131 

mixture  of  pulp  and  water  is  passed  over  a  horizontal  travel- 
ling wire  and  the  thin  sheet  of  pulp  so  obtained  drawn 
through  heavy  rollers,  which  squeeze  out  a  large  proportion 
of  the  excess  water,  and  finally  over  drying  cylinders  heated 
internally  by  steam. 

Soda  Process. — The  alkaline  treatment  of  wood  for  the 
manufacture  of  soda  wood  pulp  is  similar  to  that  used  for 
the  manufacture  of  esparto  pulp.  The  wood,  in  the  form 
of  small  chips,  is  heated  in  large  digesters  with  a  solution 
of  caustic  soda.  The  non-fibrous  constituents  of  the  wood 
are  completely  dissolved,  and  a  brown-coloured  pulp  is 
obtained.  The  spent  liquors  are  preserved  and  the  soda 
recovered,  to  be  used  over  again  as  required. 

The  soda  process  is  one  capable  of  general  applica- 
tion, being  utilised  for  woods  and  fibres  which  cannot  easily 
be  treated  by  the  sulphite  process,  which  latter  is  usually 
confined  to  the  treatment  of  the  coniferous  woods.  In  the 
early  days  of  the  manufacture  of  wood  pulp,  when  spruce 
was  available  in  large  quantities,  wood  pulp  was  almost 
exclusively  prepared  from  spruce  by  the  sulphite  process. 
The  present  scarcity  of  spruce  and  the  high  price  now 
ruling  have  compelled  manufacturers  to  give  their  attention 
to  other  classes  of  wood,  and  the  American  Government,  for 
example,  are  making  investigations  as  to  the  use  of  woods 
which  have  hitherto  been  regarded  as  unsuitable.  Such 
investigations  will,  no  doubt,  lead  not  only  to  the  introduc- 
tion of  woods  other  than  spruce,  pine,  and  poplar,  but  also 
to  modifications  in  the  various  methods  of  treatment. 

All  kinds  of  wood  and  other  fibrous  material  may  be 
converted  into  pulp  by  this  process.  Caustic  soda  combines 
with  the  acid  products  derived  from  the  non-fibrous 

K  2 


132  WOOD   PULP  AND   ITS  USES 

constituents  of  the  wood  until  the  alkali  is  neutralised,  so 
that  the  insoluble  portion  of  the  wood  left  is  cellulose  in  a 
more  or  less  pure  condition,  containing  much  less  resin 
than  the  pulp  obtained  by  the  sulphite  process. 

The  practical  operations  are  simple  enough.  The  wood 
is  barked  in  the  usual  manner  and  cut  up  into  small  pieces 
by  the  same  machinery  as  that  employed  for  the  sulphite 
process.  The  wood  is  digested  for  six  to  eight  hours  in  a 
solution  of  caustic  soda  having  a  strength  of  about  20°  Tw., 
at  a  pressure  of  1QO — 150  Ibs.  per  square  inch.  The  con- 
ditions of  treatment  are  varied  according  to  the  nature  of 
the  wood  and  the  requirements  of  the  paper  manufacturer. 
For  pulp  that  will  bleach  readily  the  process  of  digestion  is 
carried  out  to  a  greater  extent  than,  for  pulp  which  is  required 
in  the  manufacture  of  wrapping  papers.  The  yield  of  pulp 
and  the  quality  are  influenced  by  these  conditions. 

Some  interesting  experiments  were  made  by  Beveridge 
showing  the  precise  influence  of  varying  factors.  He  made 
three  sets  of  trials  as  follows  : — 


Constant  condition. 


Variable. 


1. 


2. 


3. 


Time  and  strength  of  caustic 
Pressure  and  time 

Pressure    and     strength    of 
caustic 


Pressure  varied. 
Strength  of  caustic  varied. 
Time  varied. 


The  results  were  :— 

(1)  The  increase  of  pressure  resulted  in  a  diminution  of 

yield,  the  quantity  of  pulp  obtained  being  reduced 

considerably. 


CHEMICAL  WOOD  PULP 


133 


(2)  The  excess  of  caustic  soda  caused  rapid  diminution 

in  the  yield  of  cellulose. 

(3)  The  gradual  exhaustion  of  the  caustic  soda  by  a  pro- 

longed digestion  prevented  such  serious  diminution 

of  yield. 

From  a  practical  standpoint  the  chief  consideration  is 
the  nature  of  the  wood,  and  De  Cew  gives  the  following 
results  as  showing  the  usual  conditions  of  treatment :— 


Wood. 

Weight  of 
one  cord 
128  cub.  ft. 
Lbs. 

Caustic  soda 
used  per 
cord. 

Weight  of  air- 
dry  pulp 
from  one 
cord. 
Lbs. 

Yield  air-dry 
pulp. 
Per  cent. 

1.  Yellow  Birch      . 

3630 

641 

1610 

44-4 

2.  Soft  Maple 

3520 

641 

1560 

44-4 

3.  White  Birch       . 

3190 

603 

1490 

46-7 

4.  Poplar 

2350 

603 

1150 

49-0 

5.  Bass  wood  . 

2325 

603 

1133 

49-0 

6.  Black  Spruce      . 

2250 

678 

1000 

44-5 

7.  Hemlock    , 

2300 

716 

970 

42-2 

The  variation  in  the  quality  of  the  pulp  produced  by  the 
soda  process  is  a  striking  illustration  of  the  necessity  for 
an  exhaustive  study  of  the  whole  process  of  chemical  wood 
pulp  manufacture.  The  most  interesting  developments  are 
seen  in  the  suggestion  that  the  highest  yield  of  pulp  consis- 
tent with  the  complete  removal  of  the  non-cellulose  portion 
of  the  wood  is  best  obtained  by  modifications  in  the  process, 
which  reduce  the  action  of  the  caustic  soda  on  the  cellulose 


134  WOOD   PULP  AND  ITS   USES 

to  a  minimum.  Suggestions  have  been  made  in  this  direc- 
tion not  only  with  the  soda  process,  but  with  all  chemical 
methods  by  the  idea  of  using  wood  in  a  perfectly  dry 
condition ;  by  having  a  vacuum  inside  the  digestor,  so 
that  the  air  is  largely  removed  from  the  pores  of  the 
wood,  enabling  the  liquor  to  penetrate  quickly ;  by  the 
use  of  superheated  steam  for  the  boiling  operation ;  and 
so  on. 

All  these  improvements  are  in  the  right  direction,  because 
the  wood  is  not  subjected  to  a  more  severe  treatment,  but 
is  merely  placed  under  more  favourable  conditions  for  the 
action  of  the  caustic  soda.  The  result  of  these  various 
improvements  is  seen  in  the  fact  that  many  hard  woods 
can  be  reduced  to  the  conditions  of  an  easy  bleaching 
pulp  in  three  and  a  half  to  four  hours.  Another  instance 
of  the  value  of  modified  conditions  is  to  be  seen  in  kraft 
papers. 

Kraft  Paper. — The  term  "  kraft,"  meaning  strength,  has 
been  applied  to  certain  strong  wrapping  papers  made  by 
submitting  wood  to  a  modified  soda  process.  The  paper  is 
remarkably  tough,  possesses  a  high  tensile  strength,  and  is 
a  striking  testimony  to  the  possibilities  of  wood  pulp  as  a 
material  for  making  a  great  variety  of  papers.  It  is  said 
that  the  process  was  discovered  accidentally  by  a  pulp 
manufacturer  who,  rather  than  waste  some  soda  pulp  which 
had  not  been  sufficiently  digested,  placed  the  half-boiled 
wood  in  an  Edge  runner  or  Kollergang,  and  reduced  it  to 
pulp  by  the  simple  process  of  friction.  The  paper  finally 
obtained  proved  to  be  so  firm  and  strong  that  the  success 
of  the  new  "  discovery  "  was  assured. 

The  process,  as  usually  carried  out,  involves  the  digestion 


CHEMICAL  WOOD   PULP  135 

of  the  wood  in  a  soda  or  sulphate  liquor  containing  about 
30  per  cent,  of  the  black  lye  from  some  previous  cook. 
The  wood  is  not  completely  boiled,  but  digested  to  a 
point  at  which  the  fibres  can  be  disintegrated  by  simple 
friction.  The  undissolved  ligno-cellulose  acts  as  a  useful 
cementing  material,  and  the  paper  is  bulky,  light  and 
strong. 

The  success  of  the  so-called  "  kraft  "  papers  made  from 
soda  pulp  has  led  to  the  production  of  imitations,  manufac- 
tured chiefly  from  sulphite  pulps.  The  true  kraft  papers 
may  be  distinguished  from  the  imitations  by  various 
differences  in  appearance  and  behaviour.  The  sulphite 
papers  have  a  smooth,  shiny  surface  when  viewed  in 
reflected  light  and  held  up  on  a  level  with  the  eyes,  but  this 
is  only  appreciated  by  a  practised  observer.  The  soda 
papers  are  tougher  and  capable  of  resisting  a  greater 
amount  of  friction,  as  may  be  proved  by  the  well-known 
crumpling  test.  They  can  be  twisted  repeatedly  without 
producing  fracture,  and  this  is  a  desirable  feature  in  papers 
used  for  the  manufacture  of  bags.  The  behaviour  on  tear- 
ing is  generally  different  in  the  two  papers,  the  soda  being 
more  resistant. 

The  sulphite  papers  have  a  lower  tensile  strain,  as  a 
rule,  than  soda  papers  of  equal  weight,  and  also  a  lower 
percentage  stretch  or  elongation  under  tension. 

These  differences  in  physical  qualities  may  be  used  as  a 
means  of  discriminating  between  real  and  imitation  kraft 
papers. 

It  may  further  be  noted  that  the  natural  self-colour  of 
soda  kraft  papers  is  artificially  imitated  in  the  sulphite 
krafts  by  the  use  of  yellow  aniline  dyes,  which  can  be 


136  WOOD   PULP   AND   ITS  USES 


readily  extracted  by  means  of  hot  water,  weak  solutions  of 
alkali,  or  rectified  alcohol.  The  paper  after  treatment  is 
quite  another  colour,  and  this  in  itself  is  evidence  of  a 
useful  character. 

If  small  pieces  of  the  paper  are  pulped  and  boiled  in  a 
solution  of  malachite  green,  the  soda  paper  is  dyed  to  a 
much  darker  colour  than  the  sulphite. 

When  the  pulp  is  examined  under  the  microscope,  the 
pitted  cells  in  the  fibres  of  the  soda  pulp  contain  a  little 
nucleus  of  green  colour,  which  is  easily  detected.  This 
test  is  not  of  much  value,  since  many  of  the  fibres  even  of 
the  soda  pulp  do  not  show  any  strongly  marked  pitted 
vessels. 

Soda  Recovery.— Ill  the  treatment  of  wood  and  other 
fibres  by  the  soda  process,  at  least  50  per  cent,  of  the 
weight  of  raw  material  is  dissolved,  the  yield  of  paper 
pulp  being  about  45 — 50  per  cent.  The  soluble  soda 
compounds  formed  during  the  operation  are  rich  in  organic 
matter,  and  advantage  is  taken  of  this  fact  to  recover  the 
soda  used.  The  black  liquors  discharged  from  the  digester 
are  stored  in  tanks,  together  with  much  of  the  water  used 
for  washing  the  boiled  pulp,  and  then  concentrated  by  some 
system  of  evaporation.  When  the  liquors  are  sufficiently 
concentrated,  a  thick  pasty  mass  is  obtained  containing  a 
large  proportion  of  organic  resinous  matter,  and  this  on 
being  submitted  to  the  action  of  a  furnace  catches  fire  and 
burns.  The  substance  is  thereby  converted  into  a  dry 
burning  mass,  and  after  the  combustion  is  completed  the 
resultant  material  consists  mainly  of  impure  carbonate 
of  soda. 

The  whole  process  is  one  that  calls  for  considerable  skill 


CHEMICAL  WOOD   PULP  137 

and  attention,  particularly  in  the  methods  employed  for 
utilising  all  the  available  heat.  The  cost  of  evaporation  of 
the  liquors  and  subsequent  combustion  of  the  black  liquor 
is  reduced  to  a  minimum  by  a  carefully  regulated  system  of 
washing  in  order  to  prevent  the  accumulation  of  a  large 
volume  of  weak  washing  waters,  and  by  the  utilisation  of 
the  waste  heat  obtained  by  the  combustion  of  the  organic 
soda  compounds  in  the  concentrated  liquor. 

The  following  description  of  a  modern  recovery  plant  will 
afford  some  idea  of  the  process. 

When  the  digestion  of  the  wood  or  fibre  is  complete,  the 
hot  black  lye  is  discharged  from  the  digestors  into  storage 
tanks,  which  are  usually  fixed  above  the  combustion 
chambers  so  as  to  maintain  the  temperature  and  prevent 
loss  of  heat.  The  fibrous  material  in  the  digestor  is  then 
washed  with  hot  weak  washings  from  some  previous 
boiling,  and  lastly  with  hot  clean  water.  The  final 
washings  only  contain  a  small  percentage  of  soda,  and 
these  are  utilised  as  far  as  possible  for  a  preliminary 
treatment  of  fibre  from  which  the  strong  black  lye  has 
just  been  removed.  The  systems  of  washing  vary  in 
different  mills,  but  the  main  object  is  the  same  in  all 
cases,  viz.,  a  maximum  recovery  of  the  soluble  soda  com- 
pounds with  a  minimum  volume  of  water. 

The  evaporation  of  the  black  lye  is  effected  by  the  use  of 
a  Porion  furnace  or  a  multiple-effect  evaporator. 

The  Porion  Evaporator  consists  of  a  number  of  shallow 
pans  built  of  brick,  arranged  in  the  form  of  an  enclosed 
chamber,  on  the  top  of  which  are  placed  the  tanks  contain- 
ing the  liquor  to  be  treated.  A  furnace  at  one  end  supplies 
heat,  which  sets  fire  to  the  concentrated  liquor  in  the 


138  WOOD   PULP  AMD   ITS   USES 

adjacent  pan,  and  the  heat  derived  from  the  combustion  oi 
the  thick  lye  is  utilised  in  further  evaporation  of  the  liquor 
in  the  other  pans  and  chambers.  The  Porion  is  in  effect  an 
evaporator  and  incinerator. 

The  Multiple  -  effect  Evaporator  is  based  upon  the 
systematic  utilisation  of  heat  and  reduction  of  pressure  in 
the  containing  vessels,  in  series,  so  as  to  produce  maximum 
vaporisation  effect  per  thermal  unit.  The  spent  liquors  are 
pumped  through  a  series  of  tubes  contained  in  several 
cylindrical  vessels,  the  tubes  of  the  first  vessel  being  treated 
externally  by  steam  at  a  pressure  of  15 — 20  Ibs.  The 
liquor  passing  through  the  tube  is  raised  to  boiling  point, 
and  on  being  discharged  into  a  separating  chamber  gives  up 
the  steam  produced.  The  steam  so  liberated  then  becomes 
the  heating  agent  for  the  series  of  tubes  in  the  second 
cylindrical  vessel,  and  the  partly  concentrated  liquid  falling 
to  the  bottom  of  the  separating  chamber  is  drawn  by  a 
vacuum  through  the  tubes  of  the  second  vessel,  which  are 
therefore  under  reduced  pressure.  The  process  is  repeated 
through  three  or  four  systems  of  tubes,  in  each  case  the 
steam  liberated  in  the  separating  chamber  being  used  to 
produce  a  further  concentration  of  the  liquor. 

An  apparatus  of  this  kind  will  reduce  2,000  gallons  of 
liquor  per  hour,  having  a  specific  gravity  of  T050  to  400 
gallons  with  specific  gravity  T250,  evaporating  off  1,600 
gallons  of  water  per  hour. 

The  concentrated  liquor  leaving  the  evaporator  is  dis- 
charged into  storage  tanks  and  then  allowed  to  flow  continu- 
ously into  a  rotary  furnace.  The  thick  lye  catches  fire, 
burns  with  a  steady  flame,  and  is  discharged  as  a  black 
mass  still  burning,  which  is  wheeled  away,  and  allowed  to 


CHEMICAL  WOOD   PULP  139 

char  until  the  black  carbonaceous  matter  has  completely 
burnt  off. 

Sulphate  process. — First  introduced  by  Dahl  in  1883,  for 
the  treatment  of  straw,  but  now  considerably  applied  to 
coniferous  woods  which  do  not  soften  under  the  soda  treat- 
ment as  the  foliage  of  dicotyledenous  woods. 

Sulphate  of  soda  from  which  the  process  derives  its  name 
is  of  course  inert,  i.e.  without  action  upon  the  wood  sub- 
stance and  is  added  as  a  source  of  alkali,  and  to  make  good 
the  mechanical  losses  in  the  process  of  recovery  of  the 
soda. 

This  loss  is  approximately  10  per  cent.  From  an 
analysis  of  sulphate  liquor  (see  later)  it  is  seen  that  there 
is  a  large  proportion  of  sodium  sulphide  ;  this  is  not  added 
as  such,  but  is  formed  by  the  reduction  of  the  sulphate 
to  sulphide  in  the  process  of  recovery  when  the  residue  is 
ignited,  this  reduction  being  effected  by  the  soluble  organic 
matter  in  combination  with  soda. 

The  sulphide  has  a  hydrolysing  action,  similar  in 
character  to  caustic  soda,  but  has  another  function  in 
that  it  has  the  effect  of  aiding  the  splitting  of  the  lignone 
complex  from  the  cellulose  proper.  This  dissociating 
characteristic  is  clearly  seen  when  wood  is  treated  with 
a  mixture  of  sodium  sulphide  and  hydrate,  as  against 
caustic  alone  of  the  same  soda  content. 

The  general  manufacture  of  sulphate  pulp  is  restricted, 
for  though  the  process  yields  an  excellent  pulp,  yet  the  evil 
smelling  compounds  formed  by  the  interaction  of  the 
sodium  sulphide  with  the  organic  matter,  limits  its  pro- 
duction to  sparsely  populated  districts,  as  in  Germany  and 
Austria. 


140 


WOOD   PULP  AND  ITS   USES 


ANALYSIS  OF  SULPHATE  LIQUOR. 


Sodium  sulphate 
Caustic  soda     . 
Sodium  sulphide 
Sodium  carbonate 
Sodium  acetate 


37  per  cent. 
24  per  cent. 
•28  per  cent. 
8  to  10  per  cent. 
2  to  3  per  cent. 


Soda  and  Sulphite  Pulps. — Although  at  one  time  th< 
woods  employed  for  the  production  of  sulphite  pulps  were 
almost  exclusively  pine  and  spruce,  and  the  soda  process 
was  applied  chiefly  to  poplar  and  dicotyledonous  woods,  the 
two  processes  are  now  used  almost  indiscriminately  for  any 
wood  capable  of  yielding  a  paper-making  fibre. 

It  is  exceedingly  difficult  to  differentiate  the  processes  by 
an  examination  of  the  chemical  or  microscopical  character- 
istics of  the  fibres  or  the  pulp,  especially  when  the  pulps 
have  been  bleached.  There  are  certain  broad  distinctions 
between  pure  unbleached  soda  and  unbleached  sulphite 
pulps  which  can  be  readily  noted,  but  these  are  not  easily 
detected  in  papers  containing  a  mixture  of  the  two. 

It  is  impossible  to  state  with  any  certainty  that  a 
bleached  soda  paper  does  not  contain  sulphite  pulp, 
though  any  marked  deviation  from  qualities  expected  in 
a  soda  paper  would  indicate  the  presence  of  sulphite  pulp. 
If  the  soda  pulp  has  been  made  from  poplar  wood,  it  is 
easily  detected,  and  the  admixture  of  any  spruce  may  be 
approximately  determined,  but  if  the  soda  pulp  has  been 
made  from  spruce,  no  satisfactory  analysis  is  possible. 

The  differences  between  soda  and  sulphite  pulps,  even 
when  prepared  from  the  same  type  of  wood,  may  be  found 
in.  the  physical  qualities,  since  the  soda  pulp  is  of  a  light 


CHEMICAL  WOOD   PULP  141 

brown  colour,  soft  and  bulky,  and  very  tenacious,  while 
the  sulphite  pulp  is  reddish  white,  harsh,  strong  and 
less  bulky.  The  presence  of  a  much  larger  percentage 
of  natural  wood  resin  in  sulphite  pulp,  namely,  0*5  per 
cent.,  as  against  0*05  per  cent,  in  soda  pulp,  can  be  used 
as  the  basis  of  a  test,  but  it  is  of  no  value  for  sized 
papers. 

A  small  quantity  of  the  pulp  is  heated  continuously 
with  carbon  tetrachloride.  The  solution  placed  in  a  fresh 
test  tube  is  mixed  with  an  equal  volume  of  acetic  anhydride, 
cooled,  and  added  to  a  few  drops  of  concentrated  sulphuric 
acid.  With  soda  pulp  no  definite  reaction  occurs,  but  with 
sulphite  pulp  a  pink  coloration  changing  quickly  to  green 
is  produced. 

THE  BLEACHING  OF  WOOD  PULP. 

Two  methods  are.in  use  for  the  bleaching  of  wood  pulp, 
the  most  general  being  the  employment  of  ordinary  bleach- 
ing powder,  and  the  second  being  the  treatment  of  the  pulp 
by  means  of  solutions  of  h^pochlorite  of  soda  or  magnesia 
prepared  by  electrolysing  the  chlorides.  This  method  of 
electrolytic  bleaching  is  finding  general  favour  amongst 
manufacturers  when  the  power  required  can  be  supplied  at 
a  cheap  rate. 

Bleaching  with  Chloride  of  Lime. — The  general  principle 
of  bleaching  wood  pulp  by  means  of  a  clear  solution  of 
ordinary  chloride  of  lime  is  simple  and  fundamentally  a 
process  of  oxidation.  The  method  consists  in  immersion  of 
the  pulp  in  a  given  quantity  of  diluted  bleach  liquor  of 
definite  strength,  but  many  modifications  of  method  are 
available,  and  need  to  be  closely  studied  in  order  to  produce 


142  WOOD   PULP  AND  ITS  USES 


the  best  results  economically.  The  various  systems  in  use 
may  be  briefly  described. 

Bleaching  in  the  Potcher.  —  This  is  the  process  most 
generally  adopted  by  the  paper-makers.  The  sheets  of  dry 
pulp  are  put  into  the  potcher  with  water,  broken  up,  and 
a  definite  volume  of  clear  bleach  liquor  is  added.  The  pulp 
is  continuously  circulated  until  the  desired  colour  has  been 
obtained,  or  until  the  bleach  has  been  completely  exhausted. 

When  the  operation  is  completed,  the  pulp  is  washed  con- 
tinuously with  fresh  water,  the  exhausted  bleach  liquor  and 
washings  being  removed  in  the  usual  way  by  means  of  the 
drum  washer.  In  many  cases  the  pulp  is  discharged  into 
large  tanks  provided  with  perforated  false  bottoms  and  the 
washing  process  completed  by  draining. 

Bleaching  in  Drainers. —  A  modification  of  the  above 
process  which  gives  good  results  is  frequently  .used.  The 
pulp  is  broken  up  in  the  potcher,  the  requisite  amount  of 
bleach  liquor  is  added  and  the  contents  of  the  potcher  at 
once  discharged  into  tanks  where  the  bleaching  process  is 
allowed  to  proceed  with  the  mass  at  rest.  This  method 
requires  longer  time,  but  gives  excellent  results  in  point  of 
colour  and  economy  of  bleach. 

Bleaching  by  the  Tower  system. — For  this  process  of  con- 
tinuous bleaching  a  series  of  cylindrical  vessels  with  taper- 
ing bases  is  used,  about  16  to  20  feet  high  and  8J  feet  in 
diameter. 

The  stuff  is  kept  in  circulation  by  means  of  a  pump  fitted 
at  the  junction  of  the  tapering  ends  with  an  external  pipe, 
the  latter  being  so  arranged  that  the  circulating  stuff  can  be 
pumped  into  the  tower  or  to  the  adjacent  one  of  the  battery. 

Fitted  in  the  upper  part  of  the  tower  is  a  cone,  arranged 


THE  BLEACHING  OF  WOOD  PULP  143 

centrally  with,  and  almost  touching,  the  sides  of  the  outer 
cylinder  to  ensure  thorough  distribution  of  the  stuff,  as  it 
is  pumped  up  the  external  pipe  (see  Fig.  19). 

It  is  usual  in  a  modern  battery  of  bleaching  towers  to 
pass  the  stuff  as  it  comes  up  from  the  potcher  through 
a  concentrator  in  order  to  remove  a  large  proportion  of 
water  whereby  the  bleaching  is  carried  out  more  economic- 
ally and  expeditiously. 

In  series  with  the  last  bleaching  tower  'also  there  is  a 


FIG.  19.— Tower  Bleaching  Plant. 

This  photograph  on  a  reduced  scale  represents  a  plant  capable  of 
bleaching  10  tons  of  half  stuff  per  diem. 

second  concentrator,  which  removes  the  residual  bleach 
liquor  to  a  great  extent,  the  necessary  washing  being 
reduced  thereby  to  a  minimum. 

This  machine  is  very  simple  and  compact,  and  capable 
of  a  large  output. 

It  is  on  this  account  to  a  certain  extent  replacing  the 
more  costly  presse-pate  system  of  purification.  It  consists 
of  a  revolving  drum  made  with  a  central  internal  cone,  so 
as  to  deliver  water  at  both  ends.  The  shell  itself  is  of 
brass,  drilled  with  holes  and  covered  with  a  wire  cloth. 
The  stuff  is  pumped  up  through  a  butterfly  throttle  valve 


144  WOOD   PULP   AND  ITS  USES 

into  a  splaying  mouth,  thus  causing  the  pulp  to  flow  along 
the  whole  width  of  the  drum  cover. 

The  cover  or  hood  is  so  arranged  by  means  of  packing, 
that  the  water  in  the  half-stuff  can  be  forced  through  the 
wire  cloth  of  the  revolving  drum,  by  a  pressure  of  2  to  3  Ibs. 
per  square  inch,  leaving  a  mat  of  fibre  upon  it. 

The  pulp  is  then  picked  off  the  wire  by  means  of  a 
jacketed  couch  roll,  and  a  wooden  doctor  fitted  to  the  latter 
serves  to  scrape  off  the  fibre  into  boxes.  An  economy  of 
about  25  per  cent,  in  the  bleach  consumption  over  the 
ordinary  method  employed  with  a  minimum  of  power  is 
claimed  by  this  system.  The  total  time  occupied  in  bleach- 
ing is  usually  about  twelve  hours  without  heat. 

Automatic  Process.  —  In  many  wood  pulp  mills  the 
"tower"  system  is  so  contrived  as  to  produce  a  con- 
tinuous automatic  bleaching  of  the  pulp.  The  pulp  dis- 
charged from  the  digesters  is  thoroughly  washed  and  then 
pumped  into  a  series  of  large  cylindrical  vessels,  so  arranged 
that  a  continuous  stream  of  pulp  and  water  enters  the  first 
vessel  together  with  a  carefully  regulated  quantity  of  bleach 
liquor  which  also  flows  into  the  first  tank  at  a  constant  rate. 
The  mixture  gravitates  into  the  second  vessel  of  the  series, 
then  into  the  third,  and  in  this  way  through  all  the  vessels, 
until  on  reaching  the  last  tank  the  bleach  is  fully  exhausted 
and  the  pulp  has  attained  the  desired  colour.  The  bleached 
pulp  is  then  removed  and  thoroughly  washed. 

Conditions  for  Economical  Bleaching. — It  is  difficult  to 
accurately  compare  the  methods  adopted  by  paper-makers  in 
bleaching  wood  pulp  for  the  purpose  of  determining  which 
system  gives  the  best  results,  but  there  are  certain  conditions 
common  to  all  methods. 


THE  BLEACHING  OF  WOOD  PULP 


145 


In  the  first  place,  the  bleaching  powder  must  be  of  good 
quality,  containing  the  specified  percentage  of  available 
chlorine.  The  extraction  of  the  soluble  calcium  hypo- 
chlorite  also  needs  careful  attention,  as  serious  losses  fre- 
quently occur  when  the  powder  is  not  properly  exhausted. 

With  chloride  of  lime  containing  35  to  36  per  cent,  of 
available  chlorine  the  quantity  of  clear  bleach  liquor 
obtainable  for  various  densities  is  shown  in  table  :— 

LBLE    SHOWING    THE    NUMBER     OF     GALLONS    OF    BLEACH    LlQUOR 

OBTAINED  FROM  1   CWT.  OF  POWDER   (34  TO   36  PER   CENT. 
OF  CHLORINE). 


Twaddell. 


20 

19 

18 

17 

16 

15 

14 

13 

12 

11 

10 

9 

8 

7 

6 

5 

4 

3 

2 

1 


Available  chlorine. 
Lbs.  per  100  gallons. 

Gallons  from  1  cwt. 
34  per  cent,  powder. 

Gallons  from  1  cwt. 
36  per  cent,  powder. 

61-50 

61-2 

66-0 

58-40 

65-3 

69-0 

55-18 

69-0 

73-0 

52-27 

73-5 

77-0 

48-96 

77-7 

82-5 

45-70 

84-0 

88-25 

42-31 

90-0 

97-5 

39-11 

98-3 

104-2 

35-81 

106-4 

112-5 

32-68 

116-5 

120:5 

29-61 

129-0 

137-2 

26-62 

142-0 

151-5 

23-75 

160-3 

169-7 

20-44 

186-1 

197-2 

17-36 

219-5 

232-4 

14-47 

264-0 

278-6 

11-44 

334-0 

352-5 

8-48 

448-2 

475-5 

5-58 

681-0 

722-6 

2-71 

1403-0 

1488-0 

1-40 

2725-0 

2883-0 

Any  deviation  from  the  above  figures  may  be  traced  to  an 
mecessarily  prolonged  agitation  of  the  powder  with  water 
W.P.  L 


146  WOOD  PULP  AND  ITS  USES 

or  an  imperfect  washing  of  dregs.  Fifteen  minutes  is 
sufficient  to  produce  a  liquor  -of  maximum  density  with  a 
residue  which  settles  readily  ;  if  the  operation  is  continued, 
as  it  often  is,  for  an  hour  or  more,  the  insoluble  residue 
becomes  bulky  and  does  not  settle  quickly.  The  result 
is  that  the  first  strong  liquor  cannot  be  so  completely 
siphoned  off  from  the  residue.  The  best  plan  is  to  exhaust 
for  fifteen  minutes,  allow  the  sediment  to  settle  completely, 
siphon  off  as  much  as  possible,  and  to  agitate  the  residue 
for  another  fifteen  minutes  with  fresh  water,  adding  the 
weak  liquor  when  clear  to  the  first  extract,  so  as  to  give 
a  stock  bleach  liquor  for  use  in  the  mill  at  a  density  of 
6°  Tw.  The  dregs  are  again  exhausted  with  water  and 
the  weak  liquor  so  obtained  utilised  in  exhausting  the  next 
batch  of  powder. 

It  should  also  be  noted  that  fresh  liquors  cannot  be  kept 
indefinitely  in  store  tanks  without  deterioration. 

The  unstable  nature  of  solutions  of  bleaching  powder, 
and  the  loss  of  available  chlorine  entailed  when  the  liquor 
is  not  used  under  proper  conditions,  is  well  known  to  most 
paper-makers,  although  such  depreciations  in  bleaching 
value  are  not  always  expressed  in  numerical  terms.  The 
following  experiment  will  throw  some  light  on  the  character 
and  extent  of  the  changes  found  in  ordinary  bleach  liquor, 
when  stored. 

Some  fresh  bleaching  powder  was  taken,  and  a  solution 
made  by  extraction  with  distilled  water,  having  a  strength 
of  7°  Tw.  Three  samples  of  liquor  were  put  aside  under 
the  following  conditions  : — 

A.  Sample  of  clear  liquor  in  stoppered  bottle. 

B.  Sample  of  liquor  in  an  open  vessel,  and  left  exposed, 


THE  BLEACHING  OF  WOOD  PULP 


147 


the  crust  of  chalk  which  quickly  formed  on  the  surface 
being  left  undisturbed. 

C.  Sample  of  liquor  in  an  open  vessel,  agitated  twice  a 
day,  at  9  a.m.  and  4  p.m. 

These  solutions  were  tested  once  a  week,  with  a  standard 
lecinormal  solution  of  arsenic. 

TABLE  SHOWING  C.C.  OF  ARSENIC  SOLUTION  KEQUIRED  BY 
1  C.C.  OF  THE  BLEACH  LIQUOR. 


Period. 

A. 

Stoppered 
bottle. 

B. 

Open  vessel, 
not  disturbed. 

c. 

Open  vessel, 
agitated. 

At  start  .         . 

7-05 

7'05 

7-05 

After  1st  week 

6-90 

6-90 

3-90 

„     2nd   „ 

6'85 

6-60 

0-40 

„     3rd    „             .         . 

6-8 

4-0 

0-27 

„     4th    „             .         . 

6-8 

2-7 

0-15 

In  the  case  of  the  bleach  liquor  preserved  in  a  bottle  and 
kept  away  from  contact  with  air,  the  loss  of  available 
chlorine  is  very  slight.  In  the  open  vessel,  where  the 
formation  of  a  crust  has  prevented  continual  contact  with 
air,  the  reduction  of  strength  is  slight  the  first  two  weeks. 
Probably  the  rapid  fall  in  the  later  weeks  of  the  period 
may  be  due,  in  some  measure,  to  the  disturbance  of  the 
crust  in  removing  samples  for  titration.  In  the  case  of  the 
solution  agitated  each  day  the  loss  of  strength  is  very  rapid. 

The  precise  value  of  these  changes  are  readily  seen  by 
reference  to  the  accompanying  tables,  in  which  the  losses 
are  set  out. 

L  2 


148 


WOOD   PULP  AND   ITS   USES 


TABLE  SHOWING  AVAILABLE  CHLORINE  IN  100  C.C.  OF 
THE  BLEACH  LIQUOR. 


A. 

Grammes. 

B. 

Grammes. 

C. 

Grammes. 

At  start  .... 

2-50 

2-50 

2-50 

After  1  week  . 

2-45 

2-45 

1-38 

,,     2  weeks  . 

2-43 

2-34 

0-14 

„     4      „      . 

2-40 

0-96 

0-05 

Expressing  these  results  in  a  form  more  familiar  to 
paper-makers — that  is,  in  terms  of  the  weight  of  normal 
bleaching  powder — we  get  the  following : — 

TABLE  SHOWING  THE  AVAILABLE  CHLORINE  EXPRESSED  AS  LBS. 
OF  NORMAL  BLEACHING  POWDER  PER  100  GALLONS. 


A. 
Lbs. 

B. 

Lbs. 

c. 

Lbs. 

At  start  .... 

70-5 

70-5 

70-5 

After  1  week 

69-0 

69-0 

39-0 

,,     2  weeks 

68-5 

66-0 

4-0 

„     4      „              .         . 

68-0 

27-0 

l-o 

The  storage  of  the  bleach  liquor  in  the  paper  mill  usually 
resembles  the  conditions  of  experiment  B,  and  it  will  be 
noticed  that  the  depreciation  for  the  first  week  is  very 
slight  indeed. 


THE   BLEACHING  OF  WOOD  PULP  149 

The  principal  chemical  change  brought  about  by  exposure 
to  air  is  the  disappearance  of  calcium  hypochlorite  and 
the  increase  in  the  percentage  of  calcium  chloride,  con- 
current with  the  formation  of  a  considerable  amount  of 
chalk,  more  particularly  with  the  sample  agitated  each 
day. 

Use  of  Residual  Liquors. — The  practice  sometimes  adopted 
of  utilising  residual  liquors  washed  out  of  the  potcher  on 
the  completion  of  a  bleaching  operation  cannot  be  generally 
recommended. 

"  Back  liquors  "  may  be  reported  as  containing  "  available 
jhlorine  "  in  useful  quantity  from  the  density  as  tested  by 
the  hydrometer,  in  conjunction  with  the  occasional  applica- 
;ion  of  the  usual  chlorine  test  solution,  viz.,  starch  paste 
id  potassium  iodide.  The  latter  test,  however,  has  no 
[uantitative  value,  and  the  usefulness  of  the  hydrometer  as 
indirect  indicator  of  chemical  strength  depends  upon  the 
>rrect  interpretation  of  density.  Direct  chemical  tests  are 
done  able  to  reveal  the  actual  condition  of  the  back 
Liquors. 

Circumstances  under  which  residual  liquors  could  be 
ised  with  any  advantage  are  to  be  found  in  mills  where 
fater  is  scarce.  In  such  cases  the  pulp  from  boiling  opera- 
tions might  be  treated  with  the  residues  for  the  purpose  of 
ising  up  any  traces  of  bleach,  and  also  economising  washing 
raters. 

Composition  of  Residual  Liquors. — The  liquors  left  after 
she  bleaching  of  wood  pulp  are  of  a  complex  composition, 
contain  soluble  organic  compounds,  resinous  matters, 
irae  salts,  residual  hypochlorites  and  salts  of  higher 
>xides  of  chlorine  (acids),  e.g.,  chlorites  and  chlorates. 


150  WOOD  PULP  AND   ITS  USES 

Temperley  gives  the  analysis  of  such  a  wood  pulp  liquor 
as  follows  :— 

Lbs.  per 
1,000  gallons. 

Mineral  residues,  chiefly  calcium  chloride      126'6 
Organic  residues,  volatile  on  ignition         .       62*0 

Total  solids,  dried  at  100°  C.  .     188'6 


The   surface   scum   obtained   from   the   liquor  had   the 
following  composition  :— 

Lbs.  per 
1,000  gallons. 

Resinous  matter         .....  2*17 

Lime -80 

Moisture    . 8'90 

Fibre 2'40 

Total  14-27 


The  compounds  in  solution  in  residual  liquors  are  very 
unstable,  and  react  easily  with  the  hypochlorite  of  fresh 
bleaching  powder,  so  that  the  employment  of  washings  in 
conjunction  with  raw  bleach  solution  must  result  in  a  waste 
consumption  of  powder  per  ton  of  air-dry  pulp. 

Temperley  has  shown  this  by  some  interesting  experi- 
ments, and  we  quote  these  as  illustrating  an  important 
factor  in  economical  bleaching.  Definite  quantities  of 
bleach  solution  were  added  to  known  volumes  of  ordinary 
water,  and  similarly  to  equal  volumes  of  a  carefully  filtered 
residual  liquor  from  the  bleaching  of  a  sulphite  pulp.  Th< 


THE  BLEACHING  OF   WOOD  PULP  151 

solutions  were  tested  for  a  period  of  four  hours  at  different 
temperatures,  the  results  being  very  different  in  character. 

EXPERIMENTS  WITH  ORDINARY  WATER. 

Bleaching  powder  used. 

Solution.  Temperature         Grains  per          Lbs.  per  1,000 

used.  gallon.  gallons. 

Water  70°  Fahr.  4'20  0'60 

90°      „  4-90  0'70 

120°      „  910  1-30 

EXPERIMENTS  WITH  EESIDUAL  LIQUORS. 

Bleaching  powder  used. 

Solution.  Temperature        Grains  per         Lbs.  per  1,000 

used.  gallon.  gallons. 

Liquor  70°  Fahr.         194'20  27'70 

90°     „  248-50  35-50 

120°     „  784-00  112-00 

The  figures  here  show  that  residual  liquors,  even  if 
colourless,  are  positively  detrimental  to  efficient  bleaching. 
Practical  work  demonstrates  this,  not  only  from  the  point 
of  view  of  consumption,  but,  what  is  often  of  greater 
importance,  from  the  point  of  view  of  colour.  The  same 
defect  is  found  to  a  lesser  degree  in  the  use  of  unfiltered 
water,  or  water  coloured  by  vegetable  matter  in  solution. 

It  is  evident,  therefore,  that  the  practice  of  using  residual 
liquors  should  be  confined  to  their  use  for  partial  washing, 
and  that  they  should  not  be  used  for  diluting  strong  bleach 
liquors. 

There  are  many  interesting  and  important  details  to  be 
noted  in  connection  with  the  bleaching  of  wood  pulp.  The 
process  is  frequently  hastened  by  the  use  of  live  steam, 
which  is  blown  into  a  mixture  of  pulp  in  the  potcher.  The 


152  WOOD  PULP  AND  ITS  USES 

rate  of  bleaching  is  thus  considerably  hastened,  but  the 
practice  is  not  one  that  should  be  carried  to  an  extreme. 
The  economy  of  bleach  is  also  controlled  to  some  extent  by 
the  proportion  of  water  to  pulp.  In  some  cases  the  number 
of  pounds  of  air-dry  pulp  per  gallon  of  liquid  is  much 
lower  than  it  need  be,  and  this  usually  tends  to  a  greater 
consumption  of  bleach  powder.  The  usual  proportions 
are: — 

Air-dry  wood  pulp    .         .         .     100  Ibs. 
Amount  of  solution  in  potcher      160  gallons. 

The  bleaching  of  very  hard  sulphite  pulps  not  manu- 
factured originally  for  bleaching  may  frequently  be  assisted 
by  slight  modifications  in  the  process.  A  refractory  pulp 
may  often  be  bleached  to  a  good  colour  by  the  operation 
known  as  "  successive  bleaching."  The  pulp  is  treated 
with  a  certain  proportion  of  bleach  liquor,  which  is  then 
washed  out  and  followed  by  a  further  quantity  of  fresh 
bleach  liquor.  This  method  is  often  sufficient  to  remove 
the  yellow  tinge  found  in  half -stuff  from  poor  qualities  of 
pulp. 

Caustic  soda  may  sometimes  be  used  with  advantage  as  a 
preliminary  process  in  bleaching  hard  pulps  which  exhibit 
a  reddish  colour,  but  it  is  not  economical  to  bleach  "  low 
boiled  "  pulps,  as  the  bleach  consumption  is  too  great, 
sometimes  reading  30  per  cent.  Even  simple  washing  with 
hot  water  before  bleaching  gives  a  pulp  of  greatly  improved 
colour. 

The  improvements  due  to  preliminary  washing  may  be 
traced  to  the  presence  of  soluble  constituents,  the  nature 
of  which  is  at  present  unknown.  That  these  constituents 


THE  BLEACHING  OF  WOOD  PULP 


153 


exercise  a  considerable  influence  on  the  bleaching  may  be 
seen  from  the  following  experiment  :— 

PULP  BLEACHED  FOR  THREE  HOURS  AT  70°  FAHR. 


Conditions  of  bleaching. 

Per  cent  bleach 
consumed. 

Colour. 

Pulp  bleached  in  the  ordinary  way 
in  a  shallow  dish     .... 
Pulp  bleached  in  the  ordinary  way  in 
a  bottle  
Pulp  bleached  after  being  first  ex- 
tracted with  water 
Pulp  bleached  after  extraction  with 
water  followed  by  ether          „ 

10-8 
10-8 
12-0 
7-6 

Moderate. 
it 
Good. 
Very  good. 

The  "  time  element"  is  an  important  factor  in  many 
mills  owing  to  the  lack  of  adequate  bleaching  plant,  which 
in  many  cases  can  be  attributed  to  the  fact  that  the  output 
of  paper  is  increased  by  additional  machines,  but  that  this 
is  not  accompanied  by  the  installation  of  further  plant  for 
the  preliminary  operations.  Some  pulps  bleach  quickly 
and  readily,  while  others  occupy  a  much  longer  time.  It 
is  not,  of  course,  possible  to  determine  whether  a  pulp  will 
bleach  easily  by  mere  superficial  observation ;  this  can  only 
deal  with  the  associated  characteristics  of  the  pulps.  The 
rate  of  bleach  consumption  is  a  close  index  of  general 
bleaching  quality,  and  the  following  experiment  is  of  inte- 
rest as  showing  the  differences  between  pulps  which  do  not 
exhibit  any  great  differences  when  simply  judged  on  external 
characteristics : — 

Experiment  1. — Brand  C.  An  ordinary  soda  wood  pulp. 
50  grammes  air-dry  pulp  with  450  c.c.  bleach  liquor  at 
65°  Fahr.  (containing  bleach  solution  equivalent  to 
11*7  grammes  of  dry  bleaching  powder). 


154 


WOOD  PULP  AND  ITS  USES 


Experiment  2. — Brand  B.  A  sulphite  pulp.  About  14 
per  cent,  of  bleaching  powder,  calculated  on  the  air-dry 
weight  of  pulp,  added.  Actual  consumption  for  colour 
required  amounted  to  12*5  per  cent. 
Experiment  3. — Brand  A.  A  sulphite  wood  of  good 
colour,  requiring  a  consumption  of  8  per  cent,  of 
bleach. 

Setting  out  in  tabular  form  the  rate  at  which  the  amount 
of  dry  bleaching  powder  is  consumed,  the  following  results 
are  obtained,  expressed  in  terms  of  the  percentage  rate. 
The  total  bleach  added  is  taken  as  100,  and  the  proportions 
consumed  each  hour  are  taken  as  percentages  of  the  total  :— 

KATE  OF  CONSUMPTION. 


Hours. 

Brand  C. 

Brand  B. 

Brand  A. 

0 

•o 

•o 

•o 

1 

33-0 

— 

20-0 

2 

44-0 

30-0 

33-0 

3 

51-0 

— 

43-0 

4 

66-0 

55-0 

49-0 

5 

70-0 

— 

56-0 

6 

— 

78-0 

63-0 

7 

80-0 

90-0 

70-0 

It  will  be  noticed  that  in  none  of  these  cases  was  the 
total  bleach  consumed  in  the  seven  hours.  If  the  figures 
are  plotted  out  on  a  curve,  the  differences  in  behaviour 
become  very  clear  and  may  be  expressed  in  definite  form. 

Thus,  with  Brand  C  the  pulp  bleaches  very  rapidly 
during  the  first  hour,  and  then  bleaches  at  a  uniform  rate 
for  the  succeeding  four  hours,  and  subsequently  consumes 
bleach  very  slowly. 

In  the  case  of  Brand  B,  the  pulp  bleaches  somewhat 


THE  BLEACHING  OF  WOOD  PULP  155 

rapidly  during  the  first  hour,  and  then  the  rate  of  con- 
sumption is  quite  uniform  for  the  following  six  hours. 

Finally,  with  Brand  A  the  pulp,  in  common  with  most 
brands,  consumes  bleach  rapidly  at  first,  but  afterwards 
the  rate  of  consumption  gets  slower  and  slower. 

These  three  brands  are  typical  of  the  conditions  which 
will  occur  with  the  majority  of  pulps.  The  rate  of  con- 
sumption beyond  the  period  of  seven  hours  is  not  of 
immediate  interest  to  the  paper-maker,  but  it  is  still  a 
question  of  some  moment  in  an  investigation  of  this  kind. 

Owing  to  the  great  differences  between  pulps  as  to  their 
bleaching  qualities,  it  is  important  to  have  methods  for 
determining  the  amount  of  bleach  consumed  in  bringing 
the  pulp  to  any  desired  colour.  The  following  methods 
may  be  adopted  :— 

The  Approximate  Method  of  Determining  the  Consumption 
of  Bleach. — The  behaviour  of  the  pulp  when  brought  into 
contact  with  bleach  solution  can  be  studied  by  paper- 
makers  to  some  extent  without  special  appliances  or  chemi- 
cals, provided  they  possess  some  fairly  sensitive  balance 
and  a  few  measuring  vessels.  The  following  rough-and- 
ready  method  may  be  adopted  with  advantage  in  many 
circumstances,  although  the  results  are  only  approximate, 
and  cannot  be  accepted  as  correct  enough  for  purposes  of 
settling  any  disputes  :— 

Take  200  grammes  of  the  pulp  and  wet  out  in  warm 
water;  place  in  a  large  bottle  with  a  further  quantity  of 
water;  add  a  few  beads  or,  better,  garnets,  and  shake 
vigorously.  Most  pulps  can  be  broken  up  sufficiently  for  the 
laboratory  test  in  this  way.  Strain  off  in  a  sieve,  squeeze 
out  excess  of  water,  and  divide  the  moist  mass  into  a  number 


156 


WOOD  PULP  AND  ITS  USES 


of  equal  parts,  e.g.,  10  portions,  so  that  each  lot  represents 
20  grammes  of  the  original  air-dry  pulp.  Pulps  which  will 
not  break  up  easily  by  this  method  are  reduced  with  pestle 
and  mortar  to  the  required  condition  of  complete  disin- 
tegration. Unless  the  pulp  is  thoroughly  broken  up,  the 
mass  bleaches  unevenly  and  does  not  give  uniform  results. 

Now  to  each  portion,  in  a  convenient  open  vessel,  add 
200  c.c.  water  and  varying  quantities  of  clear  bleach  liquor 
from  mill  stock,  so  as  to  obtain  a  series  of  bleaching  tests. 
If  the  mill  stock  of  liquor  stands  6°  Tw.,  then  it  is 
sufficient  to  take  the  following  data  :— 

1  gallon  of  6°  liquor  =  J  Ib.  of  good  bleaching  powder. 

1,000  c.c.  of  6°  liquor  =  50  grammes  of  good  bleaching 
powder  ;  1  c.c.  =  '050  grm. 

From  this  assumption  it  is  possible  to  work  out  the 
several  quantities  of  liquor  required  in  the  experiment 
suggested. 

The  following  table  shows  the  necessary  volumes  of 
liquor  for  certain  percentages  of  dry  powder : — 


No. 

Grammes  of 
air-dry  pulp  in 
mixture. 

Percentage  of  dry 
bleaching  powder 
to  be  added. 

Actual  weight  of 
dry  powder 
required. 

Volume  of  bleach 
liquor  to  give  the 
weight  of  powder 
stated. 

1 
2 

20-0 
20-0 

2-0 
4-0 

0'4    grms. 
0-8 

8-0  c  c. 
16-0 

3 

20-0 

6-0 

1-20 

24-0 

4 

20-0 

8-0 

1-60 

32-0 

5 

20-0 

10-0 

2-00 

40-0 

6 

20-0 

12-0 

2-40 

48-0 

7 

20-0 

14-0 

2-80 

56-0 

8 

20-0 

16-0 

3-20 

64-0 

9 

20-0 

18-0 

3-60 

72-0 

10 

20-0 

20-0 

4-00 

80-0 

I 


THE   BLEACHING  OF   WOOD   PULP  157 

If  all  these  mixtures  are  started  simultaneously,  it  is 
only  necessary  to  stir  them  occasionally  and  to  note  the 
time  at  which  the  bleach  liquor  in  each  becomes  exhausted. 
The  time  of  exhaustion  is  determined  by  means  of  starch 
and  iodide  test  papers,  which  give  a  blue  coloration  as 
long  as  the  mixture  contains  any  available  chlorine.  The 
observer  will  then  add  another  column  to  the  above  table, 
setting  out  the  various  periods  of  exhaustion. 

This  experiment  not  only  serves  to  bring  out  clearly  the 
rate  of  consumption,  but  also  gives  information  as  to  the 
amount  of  bleach  required  to  produce  a  certain  result  in 
reference  to  colour.  For  example,  the  colour  gradually 
improves  from  test  No.  1  up  the  scale  towards  No.  10. 

In  the  case  of  a  pulp  which  requires  about  16  per  cent, 
of  dry  bleach,  the  changes  in  colour  between  tests  numbered 
7  and  8  will  be  very  slight.  Test  No.  8  may  represent  a 
maximum  of  colour  with  a  certain  percentage  of  bleach, 
which  maximum  it  may  not  be  necessary  to  reach  for  the 
particular  paper  being  manufactured.  This  is  a  matter  for 
the  paper-maker  to  decide. 

Standard  Method. — A  more  accurate  method  of  deter- 
mining the  amount  of  bleach  required  for  pulp,  and  one 
which  might  be  acceptable  as  a  standard  official  method,  is 
given  in  the  form  of  instructions  as  follows : — 

Selection  of  Samples  from  Bulk. — From  the  bales  of  pulp 
delivered  into  the  mill  select  2  per  cent,  of  the  number  of 
bales.  From  each  of  the  selected  bales  remove  one  sheet. 
The  sheets  so  obtained  should  then  be  divided  into  two 
portions,  one  of  which  is  to  be  retained  for  purposes  of 
reference  and  the  other  portion  utilised  for  the  laboratory 
test. 


158  WOOD   PULP  AND  ITS  USES 

Selection  of  Laboratory  Test  Samples. — Cut  small  strips 
\  inch  wide,  and  any  convenient  length  of  2  or  3  inches 
from  each  of  the  sheets  in  the  bulk  samples,  sufficient  to 
give  three  or  four  lots  of  about  10  grammes  each. 

Preparation  of  Bleach  Liquor. — Make  up  a  bleach  solu- 
tion containing  40  grammes  of  good  powder  per  1,000  c.c. 
This  gives  a  4  per  cent,  (vol.)  solution,  which  is  a  convenient 
working  strength.  If  40  grammes  of  good  bleaching 
powder  are  thoroughly  mixed  with  water  and  filtered,  the 
residue  being  properly  washed  and  the  nitrate  made  up  to 
1,000  c.c.,  the  final  solution  is  of  such  a  strength  that 
4  c.c.  of  standard  arsenic  solution  is  equal  to  1  c.c.  of  the 
clear  bleach  liquor.  This  figure  will  vary  according 
to  the  quality  of  the  powder  and  the  completeness  of  the 
washing  of  the  powder.  The  solution  should  be  carefully 
standardised  with  decinormal  solution  of  arsenic,  so  that 
the  percentage  of  available  chlorine  is  known,  and  the  exact 
number  of  c.c.  giving  1  gramme  of  35*5  per  cent,  bleaching 
powder,  calculated.  The  convenience  of  making  up  the 
solution  in  this  way  is  obvious.  If  we  assume  a  good 
bleaching  powder  as  one  containing  35*5  per  cent,  available 
chlorine,  then 

( '00355  grm.  Cl.  or 
1  c.c.  standard  arsenic    =    j  -Ql  grm.  bleaching 

powder. 
25  c.c.  bleach  solution  =  I/O  grm.  bleaching  powder. 

Preparation  of  Test  Sample. — Weigh  out  exactly  10 
grammes  of  the  pulp  from  the  selected  test  sample,  macerate 
and  beat  in  a  mortar  with  successive  small  quantities  of 
water,  using  for  this  purpose  50  c.c.  Place  the  mixture  in 


THE  BLEACHING  OF   WOOD  PULP  159 

a  beaker,  standing  this  in  a  water  bath,  by  means  of  which 
the  mixture  can  be  heated. 

The  object  of  using  a  measured  quantity  of  water,  50 — 
60  c.c.,  is  to  ensure  that  the  final  mixture  of  pulp  and  bleach 
contains  a  definite  proportion  of  solution  to  the  amount  of 
dry  pulp  taken  for  the  experiment,  reasons  for  which  have 
already  been  discussed. 

Bleaching. — Add  62'5  c.c.  of  bleach  liquor  to  the  contents 
of  the  tumbler,  stir  with  a  glass  rod,  and  add  47 — 50  c.c.  of 
water. 

The  proportion  of  solution  to  air-dry  pulp  varies  con- 
siderably in  different  mills.  The  average  of  figures  which 
have  been  placed  at  the  disposal  of  the  writer  would 
indicate  that  the  following  proportions  might  be  utilised  for 
purposes  of  experiment : — 10  grammes  of  air-dry  pulp  and 
160  c.c.  of  solution.  With  regard  to  the  amount  of  bleach 
liquor  used,  experience  would  suggest  taking  an  excess  of 
bleach  liquor  and  determining  the  bleach  unconsumed  in 
the  solution.  Most  pulps  can  be  treated  by  adding  bleach 
liquor  obtained  from  good  bleaching  powder  equivalent  to 
25  per  cent,  of  the  weight  of  wood  pulp  taken  for  .experi- 
ment. In  the  above  case  62*5  c.c.  of  a  good  bleaching 
solution  would  be  equivalent  to  2*5  grammes  of  powder. 
This  figure,  as  already  explained,  will  vary  slightly,  but  as 
the  value  of  the  solution  is  determined  by  means  of  standard 
arsenic,  the  variations  can  be  easily  allowed  for. 

Temperature,  etc. — Maintain  the  water  bath  at  a  tempera- 
ture of  100°  Fahr.,  stirring  the  mixture  occasionally  with  a 
glass  rod,  and  testing  the  solution  from  time  to  time  with 
starch  iodide  paper.  When  the  colour  reaches  the  required 
standard,  filter  off  the  .solution  and  wash  the  pulp. 


160  WOOD   PULP  AND   ITS    USES 

A  filter  paper  is  not  necessary  for  the  purpose  of  sepa- 
rating the  solution,  because  the  pulp,  when  thrown  into  a 
funnel,  acts  as  its  own  filter.  The  washing  should  be 
continued  until  the  filtrate  shows  no  coloration  with  starch 
iodide  paper. 

Titration  of  Filtrate. — The  amount  of  unconsumed  bleach 
in  the  filtrate  is  determined  by  means  of  standard  arsenic, 
and  thus  the  amount  of  bleach  actually  consumed  by  the 
10  grammes  of  pulp  accurately  determined.  The  amount 
of  powder  used  for  the  bleaching  of  the  pulp  is  then  a 
matter  of  calculation. 

Checking  the  Result. — If  the  amount  of  bleach  originally 
added  proves  to  be  much  in  excess  of  that  actually  consumed, 
carry  out  a  second  test,  using  bleach  liquor  containing  a 
slight  excess  above  the  equivalent  of  bleaching  powder 
shown  by  the  first  experiment. 

In  all  experiments  of  this  kind  it  is  advisable  simply  to 
use  only  a  slight  excess  of  powder,  and  if  the  appearance  of 
the  wood  pulp  gives  some  clue  as  to  the  probable  amount 
of  bleach,  the  first  experiment  will  frequently  give  the 
desired  result  without  a  check  test. 

Sample  Sheets  of  Bleached  Pulp. — By  means  of  a  small 
hand  mould  make  up  a  few  sheets  from  the  bleached  pulp, 
in  order  to  have  a  permanent  record  of  the  colour  produced 
under  the  conditions  of  the  experiment.  Attach  these 
sheets  together  with  one  or  two  pieces  of  the  original  pulp 
to  the  certificate. 

Recording  the  Colour  of  Pulp. — It  sometimes  happens  that 
with  a  series  of  pulps  bleached  under  similar  conditions  the 
sheets  vary  but  little  in  colour.  Such  small  differences 
point  to  the  necessity  of  a  method  of  recording  colour 


THE   BLEACHING  OF  WOOD  PULP  161 

more  correct  than  comparative  verbal  descriptions.  Exact 
records  are  those  of  colour  analysis  by  means  of  the  Tinto- 
meter. The  following  experiment  may  be  quoted  as  an 
example : — 

Three  varieties  of  sulphite  pulp  were  examined,  and  small 
sheets  were  made  up  from  the  three  samples  as  follows  :— 

(1)  Sheets  of  the  original  unbleached  pulp. 

(2)  Sheets  from  the  pulp  after  being  bleached  with  10 

per  cent,  of  bleaching  powder. 

(3)  Sheets  of  the  pulp  after  treatment  with  18  per  cent. 

of  the  powder. 

The  colour  analysis  of  the  samples  is  given  in  a  table. 

These  results  are  interesting  and  instructive,  as  showing 
the  gradual  elimination  of  the  non-cellulose  constituents  of 
the  pulp  and  the  exact  changes  in  colour  due  to  the  varying 
extent  of  bleaching  or  oxidising  action.  The  stages  of  colour 
ire  represented  by  the  combinations  of  the  standard  glasses 
used.  In  the  original  pulp  we  have  the  combinations  of 
red,  yellow  and  blue;  in  the  pulp  bleached  with  10  per 
cent.,  red  and  yellow  only,  and  in  the  final  product  some 
traces  of  yellow.  This  table  (see  next  page)  is  the  more 
interesting  because  the  gradual  elimination  of  the  colouring 
matter  is  expressed  in  numerical  terms. 

The  significance  of  the  colour  readings  is  naturally 
only  familiar  to  those  who  are  constantly  handling  the 
^intometer  instrument.  When  an  observer  has  become 
accustomed  to  the  depth  of  colour  of  the  various  standard 
glasses,  then  the  numerical  expression  conveys  an  accurate 
idea  of  the  colour,  so  that  after  some  practice  he  obtains  a 
lental  picture  of  the  colour  of  the  pulp  from  the  figures 
\vhich  record  the  visual  colour. 

W.P.  M 


162 


WOOD   PULP  AND   ITS  USES 


11 

•~  B 

Standard  glasses 
used. 

Visual  colour. 

Substances  examined. 

S3 

|| 

Red. 

Y  ellow. 

Blue. 

Original  pulp  — 

Black. 

Orange. 

Yellow. 

Sample  1 

1-6 

1-65 

•76 

•76 

•84 

•05 

2      . 

1-3 

1-4 

•70 

•70 

•60 

•10 

Eed. 

„       3      . 

1*55 

1-5 

•95 

•95 

'55 

•05 

Pulp  bleached 

with    10    per 

cent.  — 

Orange. 

Yellow. 

Sample  1 

•17 

•60 

•17 

•43 

2     . 

•15 

•58 

•15 

•43 

3     . 

•26 

•70 

•26 

•44 

Pulp    bleached 

with    18    per 

cent.  — 

Green. 

Yellow. 

Sample  1     . 

•26 

•01 

•01 

•25 

»        '— 

•30 

•30 

3     . 

•32 

•32 

Electrolytic  Bleaching. 

This  term,  in  its  stricter  and  more  correct  sense,  implies 
a  process  in  which  a  bleach  liquor  prepared  by  electrolytic 
methods,  is  used  as  a  substitute  for  the  calcium  hypochlorite 
solution  obtained  by  treating  ordinary  bleaching  powder 
with  water.  In  practice  this  resolves  itself  into  the  use 
of  a  sodium  hypochlorite  solution  prepared  direct  from 
common  salt  by  electrolysis. 

In  a  wider  sense  the  term  may  also  be  applied  to  the  use 
of  bleaching  powder  which  has  been  manufactured  from 


THE   BLEACHING  OF  WOOD   PULP  163 

chlorine  obtained  electrically  from  salt.  In  this  case  the 
process  is  only  an  indirect  "  electrol}7 tic  bleaching,"  since 
the  actual  bleaching  agent  is  still  ordinary  chloride  of  lime. 

In  their  relation  to  the  bleaching  of  wood  pulp  both 
systems  need  to  be  considered,  since  there  might  be  certain 
advantages  with  the  indirect-  electrolytic  treatment  in 
factories  favourably  situated. 

In  the  first  system  a  solution  of  common  salt  is  submitted 
to  the  action  of  an  electric  current,  which  decomposes  the 
sodium  chloride  and  ultimately  produces  two  substances, 
caustic  soda  and  chlorine.  These  products  interact  in  the 
solution  to  form  sodium  hypochlorite,  which  is  then  at 
once  available  for  bleaching.  Only  a  small  proportion  of 
the  salt  is  actually  converted  into  the  active  hypochlorite, 
and  the  process  depends  for  its  commercial  success  on  a 
supply  of  cheap  salt  and  electrical  power. 

In  the  second  system  a  solution  of  common  salt  is  also 
submitted  to  electrolysis,  but  the  resultant  products  of 
decomposition  are  carefully  separated,  and  not  allowed  to 
combine.  The  caustic  soda  is  drawn  off  continuously  and 
subsequently  concentrated,  while  the  chlorine  gas  is  taken 
off  and  brought  into  contact  with  dry  lime  for  the  manu- 
facture of  bleaching  powder,  or  passed  at  once  into  milk  of 
lime  and  thus  converted  direct  into  bleach  solution.  Com- 
plete decomposition  of  the  original  salt  is  effected  by  this 
means,  and  two  products  of  commercial  value  are  obtained. 
In  pulp  factories  where  wood  is  treated  by  the  so.la  process 
the  use  of  this  second  system  might  be  a  decided  advantage. 

The  process  of  electrolysis  presents  no  difficulties  in  the 
laboratory,  but  the  practical  application  of  them  for  the 
purpose  of  devising  a  commercial  and  remunerative  system 

M2 


164  WOOD  PULP  AND   ITS   USES 

for  the  manufacture  of   alkali  and  chlorine  has  proved  a 
difficult  and  costly  task. 

The  laws  of  electrolysis,  together  with  the  terms  and 
nomenclature  expressing  the  relations  of  current  to  chemical 
work,  are  mainly  due  to  Faraday.  In  regard  to  the  electro- 
lysis of  common  salt  a  current  of  one  ampere  passing 
through  a  solution  of  the  sodium  chloride  will  liberate 
1*32  grammes  of  chlorine  per  hour  and  the  equivalent 
quantity  of  caustic  soda  simultaneously. 

The  terms  usually  employed  in  reactions  relating  to 
electrolysis  are  as  follows : 

Ampere. — The  unit  of  current  or  rate  of  flow  in  terms  of 
coulombs  per  second  (infra). 

Volt. — The  unit  of  electromotive  force,  or  electrical 
pressure,  which  applied  to  a  conductor  having  a  resistance 
of  one  ohm,  will  give  a  current  of  one  ampere. 

Ohm. — The  unit  of  resistance,  which  is  that  of  a  uniform 
column  of  mercury  106'3  cm.  long,  and  mass  equal  to 
14 '45  grms. 

Coulomb. — The  unit  of  quantity,  or  the  quantity  of 
electricity  derived  from  a  current  of  one  ampere,  in  one 
second. 

Watt. — The  unit  of  power  is  the  power  of  a  current  of 
one  ampere  flowing  under  a  pressure  of  one  volt.  It  is 
equal  to  one  joule  per  second. 

Joule. — The  unit  of  work,  or  the  energy  expended  in  one 
second  by  a  current  of  one  ampere  passing  through  a 
resistance  of  one  ohm. 

Electrolysis. — The  chemical  change  of  decomposition 
produced  by  a  current  of  electricity  passing  through  a 
solution  of  a  substance. 


THE  BLEACHING  OF  WOOD  PULP  165 

Electrolyte. — A  term  applied  to  the  solution  undergoing 
electrolysis. 

Electrode. — The  terminal  conductor,  usually  carbon  or  a 
metal,  by  means  of  which  the  current  is  passed  into  or 
taken  away  from  the  solution  undergoing  electrolysis. 

Anode. — The  conductor  or  electrode  which  conducts  the 
current  into  the  solution  or  electrolyte. 

Cathode. — The  conductor  or  electrode  which  conducts  the 
current  out  of  the  solution  or  electrolyte. 

Anion. — The  product  of  electrolysis  obtained  from  the 
electrolyte  which  is  given  off  at  the  anode,  and  is  always 
electro-negative  in  character. 

Cation. — The  product  of  electrolysis  obtained  from  the 
electrolyte  which  is  given  off  at  the  cathode,  and  is  always 
electro-positive  in  character. 

Power  Consumption. — This  is  usually  measured  in  "  kilo- 
watts." 

A  watt        —  ampere  X  volt. 

A  kilowatt  —  1,000  (amperes  X  volts). 

746  watts  —  1  horse-power. 

Production  of  active  chlorine. — The  equivalent  of  one 
ampere  passing  through  a  solution  of  salt  is  1*32  grammes 
of  chlorine  per  hour  (at  the  anode).  In  practice  a  smaller 
yield  is  obtained  owing  to  secondary  reactions  and  equiva- 
lent loss  of  current  efficiency,  increasing  as  the  amount  of 
"  active  chlorine  "  accumulates.  The  actual  mean  produc- 
tion is  about  one  gramme  of  chlorine  per  ampere-hour  for 
weak  liquors.  On  this  basis  with  a  potential  of  3*5  volts, 
For  1  gramme  chlorine  =  1  ampere-hour. 

1  kilo  chlorine  =  1,000  ampere-hours. 

1016  kilos  chlorine  =  (1,000  X  1,016  X  3'5)  watts. 


166  WOOD   PULP  AND   ITS  USES 

or     1  ton  chlorine  =  3,556,000  watts. 
=  3,556  kilowatts. 

The  actual  consumption  of  power  under  the  systems  now 
in  practical  use  appears  to  be  5,000  kilowatts  for  a  ton  of 
"  active  chlorine." 

The  earliest  attempts  at  the  direct  industrial  production 
of  bleach  liquor,  i.e.  a  solution  of  a  hypochlorite,  were  made 
by  E.  Hermite  over  twenty  years  ago.  On  this  system  the 
electrolyte  was  a  solution  of  Magnesium  Chloride  (2 — 3 
per  cent.  MgCk),  which  was  electrolysed  to  a  concentra- 
tion of  about  3  grammes  "  chlorine  "  per  litre. 

An  essential  feature  of  this  process  was  the  continuous 
circulation  of  the  electrolysed  liquor  as  between  the  electro- 
lyser and  the  beating  engine,  and  the  realisation  of  the 
cycle  of  changes,  viz : — the  electrolysis  of  the  magnesium 
chloride  to  hypochlorite  in  the  electrolyser  and  its  reversal 
in  the  beating  engine  as  the  result  of  chemical  work  done. 
The  Hermite  system  on  this  principle  was  found  unwork- 
able, for,  owing  to  secondary  reactions  and  waste  consump- 
tion of  bleaching  compounds,  the  percentage  current 
efficiency  was  very  low.  It  is  still  used,  however,  as  a 
method  of  producing  a  hypochlorite  solution. 

There  are  now  several  types  of  electrolytic  apparatus  in 
use,  based  on  the  conversion  of  salt  (sodium  chloride)  into 
sodium  hypochlorite. 

Haas  and  Oettel  Apparatus. — This  electrolyser  is  simple 
in  construction  and  working,  and  is  in  considerable  favour 
where  small  quantities  of  bleach  liquor  are  required, 
particularly  in  laundries  and  textile  works.  It  consists  of 
a  narrow  earthenware  vessel  containing  the  electrodes, 
which  are  so  arranged  that  the  vessel  is  divided  into  a 


THE  BLEACHING  OF  WOOD  PULP. 


167 


number  of  separate  compartments,  provided  with  a  feed 
pipe  to  each  near  the  bottom,  and  an  overflow  channel  at 
the  top.  This  vessel  is  immersed  in  the  large  store  tank 
containing  a  salt  solution  of  10°  Be.  When  the  current 
passes,  the  hydrogen  gas  liberated  at  the  cathode  causes 
the  solution  to  froth  and  rise  up  in  each  compartment. 
This  produces  an  automatic  continuous  circulation  of  the 


FIG.  20. — Haas  and  Oettel  Electrolyser. 

electrolyte  solution,  since  the  expulsion  of  some  of  the 
latter  through  the  overflow  pipes  produces  a  partial  vacuum 
in  each  chamber,  which  causes  fresh  liquor  to  pass  into  the 
chambers  through  the  feed  pipes  at  the  bottom. 

Adequate  arrangements  of  cooling  pipes  ensure  a  com- 
paratively low  temperature  in  the  cell,  which  is  essential  to 
the  production  of  a  maximum  amount  of  hypochlorite  and 
a  minimum  amount  of  chlorate. 


168  WOOD  PULP  AND  ITS  USES 

The  current  is  maintained  until  the  desired  strength  of 
"  active  chlorine  "  has  been  obtained,  at  which  point  the 
charge  is  drawn  off  into  store  tanks,  and  a  fresh  quantity 
of  salt  pumped  into  the  apparatus.  The  process  is 
therefore  intermittent. 

The  standard  pattern  for  the  production  of  large 
quantities  of  sodium  hypochlorite  as  required  in  the  paper- 
mill  is  shown  in  Fig.  20. 

It  is  constructed  wholly  of  stoneware,  the  electrodes  are 
made  of  "  carbon,"  and  the  apparatus  is  adapted  for  a  con- 
tinuous current  at  110  volts.  The  makers  quote  the  follow- 
ing figures  as  indicating  its  output  and  economy  of  working, 
based  on  a  12  hours  test  :— 

Capacity  of  Tank  750  litres  =  166  gallons. 

Salt  used.  280  Ibs.  =  166  gallons  at  23°  Tw. 

Temperature  of  solution  20°  C. 
Current  43  amperes. 

Potential  110  volts. 

Chlorine  obtained  26'73  Ibs. 

With  these  results  the  figures  for  the  production  of   one 
ton  of  active  chlorine  are  : — 
One  cell  produces  in  one  working  day  53'0  Ibs.  chlorine. 

.     ,  110  X  43  x  24 
Power  required  -        i  QQQ        "  =  H^'6  kilowatt  hours. 

One  ton  chlorine  requires  power    =  4,800  kilowatt  hours. 

and  salt    =  10*5  tons. 

Siemens  and  Halske  Elcctrolyser. — This  apparatus  is 
already  in  use  in  several  paper-mills,  notably  the  Borregaard 
works  of  the  Kellner  -  Partington  Co.  in  Norway.  The 
electrodes  are  made  of  platinum-iridium  gauze  arranged 
horizontally  in  shallow  stoneware  electrolysers,  or  in 


THE  BLEACHING  OF   WOOD  PULP 


169 


CHLORINE  CAUSTIC   SODA   CELL 

SECTION  


A 

CARBON     ANODE 

H 

HEATING    PIPE 

AR 

ANODE    CHAMBER 

K 

IRON   WIRE   NET,    CATHODE 

6 

CONCRETE   COVER. 

K  R 

CATHODE    CHAMBER 

C 

CHLORINE    OUTLET 

N 

CAUSTIC    SODA    OUTLET. 

D 

DIAPHRAM    CLOTH. 

S 

SALT    INLET 

E 

IRON    BATH 

W 

HYDROGEN    OUTLET 

FIG.  21. 

iron  vessels  suitably  lined  with  glass  or  other  insulating 
material.  These  vessels  are  so  constructed  as  to  form  a 
series  of  small  independent  decomposing  cells,  and  the 


170  WOOD  PULP  AND   ITS  USES 

solution  of  salt  is  passed  continuously  through  the  whole 
series.  The  electrodes  are  connected  up  so  that  no 
electrical  connections  inside  the  several  electrolysers  are 
necessary.  The  bleaching  liquor  produced  is  drawn  off 
into  reservoirs,  or  kept  in  circulation  until  the  "  active 
chlorine  "  is  at  the  working  strength. 

The  makers1  of  this  apparatus  have  published  interesting 
statistics  from  time  to  time  and  give  the  following 
particulars  in  reference  to  some  works  in  Switzerland. 

At  this  mill  the  quantity  of  bleach  liquor  obtained  in  12 
hours  amounts  to  2,300  litres  containing  15  grammes  of 
active  chlorine  per  litre. 

Current  used     —  120  amperes  at  120  volts. 
Salt  consumed  =  250  kilos  in  2,300  litres  of   water 
to  give   15   grammes   chlorine   per 
litre. 

Working  out  the  cost  of  production  with  the  above  figures 
the  results  are  : — 

,  2,300  X  15 
Chlorine  produced  -  —  =  34'5  kilos. 

1,UUU 

,-,,  120  X  120  X  12 

Electrical  power    =  -  -  =  173  k.w.  hours. 

1,UUU 

Electrical  power  for  1,016  kilos  j      173  x  1  016  , 

...  \  =  -  -  k.w.  hours, 

chlorine     .         .         .         .  I  34*5 

Electrical  power  for  1  ton  chlorine  =  5,090  k.w.  hours. 

Salt  for  34'5  kilos  chlorine    =  250  kilos. 
„     ,,    1,016  kilos  chlorine  =  7,500  kilos. 
„      ,,    1  ton  chlorine  =  7*5  tons  salt. 

1  "  Papermaker's  Monthly  Journal,"  May,  1910. 


THE  BLEACHING  OF  WOOD   PULP 


171 


The  following  table  has  been  given  to  show  the  cost  of 
power  and  salt  for  one  kilogram  active  Chlorine. 


No. 

Price  per  litre. 

Cost  of  power 
for  1  kg.  active 
chlorine. 

Cost  of  salt 
for  1  kg.  active 
chlorine. 

Cost  of  power 
and  salt  for  1  kg. 
active  chlorine. 

s.    d. 

d. 

d. 

d. 

1 

1     4 

1-42 

0-72 

2-14 

1     2 

2-85 

0-72 

3-37 

0     1 

5*7 

0-72 

6-42 

2 

1     4 

1-3 

0-864 

2-164 

1     2 

2-6 

0-864 

3-464 

0     1 

5-2 

0-864 

6-064 

3 

1     4 

1-2 

1-08 

2-28 

1     2 

2-4 

1-08 

3-48 

0     1 

4-8 

1-08 

5-88 

4 

1     4 

1-15 

1-44 

2-59 

I     2 

2-30 

1-J4 

3-74 

0     1 

4-60 

1-44 

6-04 

The  Siemens  and  Halske  apparatus  is  so  constructed  that 
the  products  of  electrolysis,  namely-chlorine  gas  and  caustic 
soda,  can  be  separated  continuously  during  electrolysis,  and 
when  so  desired  caused  to  interact  outside  the  electrolyser 
for  the  production  of  bleach  liquor  direct.  The  makers 
claim  that  by  this  means  the  same  amount  of  active  chlorine 
can  be  produced  with  lesser  power  and  with  a  smaller  pro- 
portion of  salt,  and  state  that  the  power  consumption  is  3*5 
to  4  k.w.  hours  for  each  one  pound  of  active  chlorine.  It 
is  obvious  that  a  plant  capable  of  producing  bleach  and  soda 
in  this  way  possesses  many  advantages  over  those  forms  of 
apparatus  in  which  only  bleach  liquor  is  produced.  In 
localities  where  lime  is  plentiful  and  cheap,  and  where 
caustic  soda  finds  a  ready  market,  the  Siemens  and  Halske 
electrolyser  should  give  economical  results.  Taking  the 
figures  above  quoted  with  the  apparatus  utilised  only  for 


172  WOOD   PULP  AND   ITS   USES 

the  manufacture  of  bleach  liquor,  the  cost  of   one  ton  of 
active  chlorine  would  appear  to  be  as  follows :— 


Quantities. 

Price. 

Total. 

Power    . 

5,090  k.w.  hours 

at  jd.  per  unit  l 

£      s.     (1. 
5     0     0 

Salt 

7  '5  tons 

at  12s. 

4  10     0 

Renewals 

— 

say 

0  10     0 

Interest  and  other 
charges 

— 

say 

100 

£11     6     0 

1  The  unit  is  a  kilowatt  hour. 

Schuckert's  Electrolyser. — This  apparatus  consists  of  cells 
similar  to  those  employed  in  other  electrolysers,  the  chief 
feature  being  the  special  form  of  the  electrodes.  In  the 
Siemens  and  Halske  apparatus  the  electrodes  are  con- 
structed of  platinum  and  iridium,  while  in  the  Haas  and 
Oettel  they  are  provided  with  electrodes  made  entirely  of 
graphite.  In  Schuckert's  electrolysers  the  positive  electrodes 
are  made  of  platinum  and  the  negative  electrodes  of  graphite. 
This  arrangement  is  based  upon  the  fact  that  the  carbon 
electrode  is  not  attacked  by  the  electro-positive  element 
at  the  negative  pole,  and  the  platinum  is  not  acted  upon  by 
the  electro-negative  compounds  present  at  the  positive  pole. 
Several  advantages  are  claimed  for  this  arrangement,  as  not 
only  does  the  apparatus  require  less  frequent  renewels,  but 
the  presence  of  smaller  particles  of  carbon  in  the  liquid  is 
avoided.  This  electrolyser  appears  to  be  capable  of  provid- 
ing strong  solutions  of  bleaching  liquid.  With  a  10  per  cent, 
solution  of  salt  a  bleaching  liquid  containing  15  grammes  of 


. 


THE  BLEACHING  OF  WOOD  PULP 


173 


ctive  chlorine  per  litre  can  be  obtained  with  an  energy 
consumption  of  3*2  kilowatt  hours  and  a  supply  of  5'4  Ibs. 
of  salt  per  Ib.  of  chlorine.  The  usual  limit  is  20  to  22 
grammes  of  active  chlorine  to  the  litre,  and  with  a  Schuckert 
electrolyser  30  to  35  grammes  per  litre  can  be  obtained. 

Some  interesting  experiments  have  been  made  by  Dr. 
Fraass  with  electrolytic  bleach  liquor  prepared  by  the 

ihuckert  apparatus.1 

The  cellulose  examined  was  easy  bleaching  sulphite  pulp. 

weighed  quantity  of  the  pulp  was  mixed  with  water  and 

definite  proportion  of  bleach  liquor  (a)  from  chloride  of 
me  and  (I)  from  electrolytic  bleach  liquor.  The 

mperature  of  the  operation  was  maintained  at  about  30°  C. 
until  the  whole  of  the  chlorine  had  been  consumed.  The 
results  of  this  test  are  given  as  follows  :— 

COMPARISON  OF  BLEACHING  EFFECTS  OF  (a)  CHLORIDE  OF  LIME 
AND  (6)  ELECTROLYTIC  LYE. 


Test 
No. 

Pulp 
concentra- 
tion. 

Active  chlorine 
present. 
Grammes  per 
litre. 

Chlorine  used 
per  100 
grammes  of 
air-dried  pulp. 

Resulting  white. 

a 

6 

a 

6 

1 

1:15 

0-67 

0-H7 

2-00 

2-00 

Same  with  both. 

2 

1:16 

1-25 

1-25 

1-99 

1-99 

Better  with  electrolytic  lye. 

3 

1:12-7 

0-80 

0-80 

2-00 

2-00 

4 

1:12-5 

0-73 

0-73 

1-82 

1-82 

o 

1:12-5 

0-80 

0-80 

2-02 

2-02 

6 

1:12-7 

0-80 

0-80 

2-00 

2-00 

7 

1:12-7 

0-79 

0-79 

2-00 

2-00 

8 

1:20 

1-00 

1-00 

2-00 

2-00 

9 

1:20 

1-50 

1-50 

3-00 

3-00 

10 

1:20 

1-00 

1-00 

2-00 

2-00 

11 

1:20 

1-00 

1-00 

2-00 

2-00 

12 

1:20 

1-50 

1-50 

3-00 

3-00 

For  further  details  see  "Papier  Fabrikant,"  1909. 


174 


WOOD  PULP  AND  ITS  USES 


Further  experiments  were  made  by  Dr.  Fraass  to  deter- 
mine the  actual  saving  of  chlorine,  if  any,  effected  by  the  use 
of  electrolytic  chlorine.  The  following  results  were  obtained. 


(a)  REFERS  TO  CHLORIDE  OF  LIME  ;  (6)  KEFERS  TO 
ELECTROLYTIC  LYE. 


Pulp 

Active  Chlorine 

Chloripe  used 

Resulting 

Test 
No. 

concentra- 
tion. 

present. 
Grammes  per 
litre. 

per  100 
grammes  of 
air-dried  pulp. 

save  with  b 
in  per  cent. 
Chlorine. 

Better  white  with. 

a 

b 

a 

b 

14 

1:20 

1-01 

0-995 

2-02 

1-99 

1-43 

b. 

16 

1:20 

3-00 

2-99 

5-50 

5-40 

1-90 

b. 

18 

1:15 

1-27 

1-23 

2-06 

2-00 

2-90 

b. 

20 

1:16 

1-29 

1-24 

2-06 

1-99 

3-40 

b. 

22 

1:20 

2-27 

2-17 

4-54 

4-34 

4-40 

b. 

24 

1  :  20 

2-27 

2-15 

4-54 

4-30 

5-26 

a  and  b  same. 

26 

1:12-5 

0-89 

0-80 

2-21 

2-00 

10-0 

a. 

28 

1  :20 

1-00 

0-90 

2-00 

1-80 

10-0 

a. 

30 

1:12-7 

0-80 

0-71 

2-00 

1-80 

10-0 

a. 

From  the  foregoing  brief  account  of  electrolytic  bleach- 
ing systems  it  would  appear  that  evolution  on  the  basis  of 
experience  has  limited  these  systems  to  the  production  of  a 
solution  of  a  hypochlorite  which  is  used  upon  the  pulp  or 
cellulose  textile  to  be  bleached,  and  is  then  rejected  as  a 
waste  liquor  after  the  bleaching  agents  are  exhausted  in 
doing  chemical  work  upon  the  pulp  or  fabric. 

The  idea  of  an  industrial  cycle  as  advanced  by  Hermite 
is  rendered  impossible  by  the  fact,  which  is  too  often  over- 
looked, that  with  the  bleaching  or  oxidising  action  there  are 
secondary  reactions,  as  a  result  of  which  organic  products 
pass  into  solution.  These  products  will  consume  oxygen 
until  reduced  to  compounds  of  the  lowest  molecular  weight. 
This  of  course  is  entirely  waste  work. 


THE  BLEACHING  OF  WOOD  PULP  175 

The  electrolytic  systems  finally  evolved  are  therefore 
intermittent,  and  the  rejection  of  the  waste  solution  involves 
a  loss  of  so  much  salt  which  is  too  dilute  a  form  to  be  use- 
fully recovered. 

When  we  come  to  the  question  of  the  direct  production 
of  caustic  soda  and  chlorine,  we  arrive  in  the  region  of 
"  heavy  "  chemical  industry. 

As  a  result  of  inventive  evolution  there  are  two  systems 
finally  established  in  this  country,  which  are  those  of 
Castner-Kellner,  and  Hargreaves-Bird. 

Each  of  these  systems  produces  chlorine  as  such,  which 
is  converted  into  bleaching  powder,  or  bleaching  liquor,  as 
an  ordinary  chemical  operation  outside  the  electrolytic 
system. 

As  regards  the  work  of  the  cathode,  or  soda  end  of  the 
process,  the  Castner-Kellner  system  produces  caustic  soda 
owing  to  the  special  disposition  of  its  electrode,  whilst  in  the 
Hargreaves-Bird  process  the  soda  which  is  produced  as 
caustic  soda  is  removed  in  the  form  of  carbonate. 

These  well-established  systems,  for  the  production  of 
alkali  and  "  bleach,"  are  not  easily  engineered,  and  they 
are  in  many  respects  unsuitable  for  small  production. 

The  matter  with  its  technical  and  commercial  issues  is 
much  too  complicated  to  be  usefully  discussed  within  the 
scope  of  this  work. 

Many  problems  are  presented  which  are  as  yet  by  no 
means  solved  and  it  is  quite  possible  that  the  over-pro- 
duction of  chlorine,  which  is  an  incidental  feature  of  these 
systems,  may  lead  to  further  developments  of  the  industrial 
production  of  cellulose  on  very  different  lines  from  those 
which  are  exploited  to-day  as  almost  stereotyped. 


176 


WOOD  PULP  AND  ITS  USES 


IMPORTS  OF  WOOD  PULP  INTO  GREAT  BRITAIN,  1904 — 1908. 
(From  the  Annual  Statement  of  Trade  of  the  United  Kingdom). 


QUANTITIES. 

1904.             1905. 

1900. 

1907. 

1908. 

CHEMICAL,  DRY. 

Tons. 

Tons. 

Tons. 

Tons. 

Tons. 

From  Russia 

9,538 

12,179 

11,698 

13,558 

15,501 

,,      Sweden    .... 

131,65o 

133,564 

127,046 

157,916 

1  (i:5,()74 

,,      Norway  .... 

55,213 

63,948 

77,047 

70,957 

77,6(5o 

,,      Germany 

5,609 

7,186 

7,584 

15,514 

2  3,  (is  7 

,,      Netherlands    . 

2,781 

2,622 

2,595 

3,280 

1,820 

,,      Portugal 
,,      Austria  Hungary   .. 

2,115 

2,183 

2,482 
3,163 

2,219 
1,765 

2,416 
4,305 

2,170 

1,876 

,,      United  States  of  America 

1,188 

2,917 

2,691 

1,942 

855 

,,      Other  Foreign  Countries 

862 

349 

707 

300 

212 

Total  from  Foreign  Countries 

211,139 

228,410 

233,352 

270,188  286,860 

Total  from  British  Possessions 

253 

2,964 

7,297 

753 

1,795 

Total     .... 

211,392 

231,374 

240,649 

270,941 

288,655 

CHEMICAL,  WET. 
From  Sweden    .... 

Tons. 

7,112 

Tons. 
6,948 

Tons. 
7,261 

Tons. 
13,295 

Tons. 

16,310 

,,      Norway  .... 

17,673 

11,117 

9,109 

8,724 

10,976 

,,      Other  Foreign  Countries 

10 

45 

10 

Total  from  Foreign  Countries 

24,785 

18,075 

16,370 

22,061 

27,296 

Total  from  British  Possessions 

(Canada) 

19 

250 

Total    .... 

24,785 

18,094 

16,370 

22,314 

27,296 

MECHANICAL,  DRY. 

Tons. 

Tons. 

Tons. 

Tons. 

Tons. 

From  Russia      .... 

3,199 

2,776 

1,999 

1,037 

2,061 

,,      Sweden  .... 

2,984 

3,922 

1  ,936 

2,428 

3,810 

,,      Norway  .... 
,,      Other  Foreign  Countries 

2,811 
154 

3,553 
16 

2,733 
1 

2,593 
11 

2,192 
10 

Total  from  Foreign  Countries 

9,148 

10,267       6,669 

6,069 

8,073 

Total  from  British  Possessions 

(Canada) 

51 

•  • 

1,453 

Total     .   '      . 

9,199 

10,267       6,669 

6,069 

9,526 

IMPORTS   OF   WOOD  PULP  INTO   GREAT   BRITAIN    177 


QUANTITIES. 

1904. 

1905. 

1906. 

1907. 

1908, 

MECHANICAL,  WET. 

From  Russia      .... 
,,      Sweden    .         .         . 
,,      Norway  .         . 
,,      Germany 
,,      Other  Foreign  Countries 

Total  from  Foreign  Countries 

From  Canada     .... 
,,      Other  British  Possessions 

Tota'l  from  British  Possessions 
Total    .         .      •  . 

Tons. 
5,452 
30,741 
224,620 
25 
74 

Tons. 
2,614 
32,940 
202,249 
25 
182 

Tons. 
1,686 

31,212 
229,202 

'64 

Tons. 
2,899 
43,610 
262,256 
6-15 
220 

Tons. 
2,608 
46,019 
277,988 
799 

260,912 

238,010 

262,164 

309,630 

327,414 

62,957 

80,236 
31 

80,959 

63,545 

95,543 

62,957 

80,267 

80,959 

63,545 

95,543 

323,869 

318,277 

343,123 

373,175 

422,957 

CHAPTEE  VI 

NEWS    AND    PRINTINGS. 

THE  applications  of  wood  pulp,  though  large  and  of  first- 
rate  industrial  importance,  are  not  numerous.  Its  utilisa- 
tion, however,  in  paper-making  is  essentially  one  of  great 
influence,  and  in  point  of  fact  this  industry  at  the  present 
time  dominates  the  wood  pulp  market.  In  this  country 
there  have  been  several  well-marked  phases  of  expansion 
of  the  industry.  A  prominent  landmark  was  .the 
repeal  of  the  duties  on  paper  in  1860.  By  a  coincidence 
this  indirect  condition  of  expansion  synchronises  with 
the  introduction  of  esparto  grass  to  develop  rapidly  into 
an  important  staple  raw  material,  almost  a  generation 
in  advance  of  the  wood  pulp  age.  By  the  year  1880  the 
importation  of  esparto  had  reached  200,000  tons,  and  it  is 
a  somewhat  remarkable  feature  of  this  industry  that  the 
consumption  of  esparto  has  shown  no  growth  from  this 
figure. 

The  wood  pulps  have  been  independently  developed. 
"  Mechanical  "  wood  pulp  or  ground  wood  dates  back  to  the 
period  1850 — 60.  The  chemical  pulps  in  this  country  were 
pioneered  by  C.  B.  Ekman  in  collaboration  with  George  Fry 
in  the  period  1870 — 80.  This  early  venture  was  capitalised 
by  Thomson^  Bonar  &  Co.,  and  worked  at  Bergvik,  Sweden, 
and  Ilford,  Essex*  The  new  industry  attracted  other  pioneer 


NEWS  AND  PRINTINGS 


179 


workers,  notably  E.  Partingtonin  this  country,  and  C.  Kellner 
in  Austria,  who  individually  and  jointly  did  much  to 
establish  the  new  order  during  the  following  decade.  It 
requires  a  little  calculation  to  estimate  the  growth  of  the 
industry  during  this  period,  1880 — 90,  since  the  statistics 
of  importation,  in  the  Board  of  Trade  returns,  are  a  complex 
return  including  "  Esparto  and  other  Materials  "  :  it  was 
not  until  1888  that  the  returns  of  wood  pulp  importation 
were  separately  recorded.  The  growth  of  the  wood  pulp 
trade  from  1880  to  1888  represents  an  estimated  quantity 
of  100,000  tons,  and  at  this  later  date  the  industry  had 
become  widespread  and  firmly  established  in  Scandinavia, 
Germany  and  America.  The  English  importation  has 
continued  to  grow,  and  the  figures  for  the  first  nine  years 
of  the  century  may  be  cited  :— 


The  total  world's  production  of  "  chemical  pulp  "  is  fast 
approaching  3,000,000  tons.  In  taking  this  statistical  view  of 
the  paper  industry  we  may  note  the  figures  arrived  at  by 
Krawany,  for  paper  consumption  per  head  per  annum,  in 
European  countries  : — 


England 

Kg. 
25-3 

Belgium 

Kg. 
11-1 

Russia 

Kg. 
2-2 

Sweden 

24-0 

Holland      . 

10-8 

Greece 

1-8 

Finland 

22'5 

Italy  . 

7'o 

Turkey 

1-8 

Germany    * 

19'7 

Denmark    . 

6-4 

Boumania  . 

1-4 

Norway 

16-3 

Luxemburg 

4-8 

Bulgaria 

1-3 

Switzerland 

15-0 

Spain  . 

4-4 

Bosnia 

0-7 

France 

14-0 

Hungary    . 

3-6 

Servia 

0-6 

Austria 

11-1 

Portugal     . 

3-4 

Another  result  of  this  statistical  inquiry  is  the  ascertained 
annual  increase  of  the  world's  production,  which  at  5J  per 

N2 


180  WOOD  PULP  AND  ITS  USES 

cent,  is  nearly  double  the  estimated  increase  of  other  large 
manufactures,  viz.,  2f — 3^  per  cent.  These  figures  are 
taken  from  an  interesting  paper  by  Dr.  A.  Klein  on 
"  Cellulose,  Wood  Paper,  Artificial  Silk,"  recently  published 
(Chem.  Zeit.,  60,  521—530  (1910)). 

The  most  significant  development  in  the  paper-making 
art  and  industry  founded  on  wood  pulp  is  in  the  production 
of  "news,"  and  we  may  take  "News  and  Printings"  as 
the  subject  of  this  chapter,  and  typical,  in  fact,  of  the 
industrial  age  we  live  in. 

The  enormous  quantities  of  mechanical  and  chemical 
pulp  manufactured  to-day  are  used  chiefly  in  the  production 
of  "news"  and  cheap  printing  papers. 

A  modern  newspaper  contains  about  70  per  cent,  of 
mechanical  pulp  mixed  with  30  per  cent,  of  chemical  pulp. 
In  addition  to  the  fibrous  constituents  the  paper  will  also 
contain  about  8  to  10  per  cent,  of  china  clay,  and  a  small 
proportion  of  rosin  size.  As  far  as  the  paper  mill  is 
concerned,  the  process  of  manufacture  is  almost  entirely 
an  engineering  problem,  since  all  the  materials  used  are 
purchased  largely  in  a  completely  manufactured  state,  the 
object  being  to  eliminate  chemical  processes  whenever 
possible. 

This  is  only  true  of  paper  mills  dependent  on  outside 
sources  for  the  supplies  of  pulp  and  chemicals,  but  the 
tendency  of  modern  practice  in  such  mills  is  to  reduce 
the  question  to  one  of  mixing  certain  ingredients  and 
getting  the  maximum  output  of  paper  at  a  minimum 
cost* 

At  the  same  time  chemistry  plays  an  important  part  in 
the  efficient  and  economical  working  of  a  "news"  mill. 


NEWS  AND   PKINTINGS  181 

From  start  to  finish  every  process  is  controlled  by  analysis, 
while  improvements  in  the  quality  of  the  paper  are  gradually 
introduced,  either  by  the  use  of  superior  wood  pulps,  or  by 
suggestions  that  arise  from  a  careful  study  of  the  systematic 
records  kept. 

A  general  survey  of  the  operations  necessary  for  the 
production  of  this  class  of  paper  will  show  the  intimate 
relation  between  chemistry  and  engineering  in  almost  any 
industrial  process. 

Power. — The  amount  of  coal  consumed  averages  18 — 
20  cwt.  per  ton  of  finished  paper.  Most  of  this  fuel  is 
required  for  motive  power,  though  a  certain  proportion 
is  used  in  drying  the  paper  during  manufacture.  The 
steam  engine  is  employed  for  this  in  nearly  every  paper 
mill,  but  in  a  few  cases  gas  engines  worked  from  gas 
producers  have  been  tried. 

The  maintenance  of  an  extensive  boiler  plant  on  up-to- 
date  principles  demands  the  control  of  the  coal  supplies  in 
the  matter  of  weight  received,  the  analysis  of  same  for 
moisture,  ash  left  on  combustion,  and  calorific  value ;  the 
systematic  analysis  of  the  waste  gases  from  the  boiler  flues 

prevent  careless  firing  of  the  boilers,  and  to  ensure  com- 
plete combustion ;  the  use  of  suitable  water  for  boiler 
purposes,  involving  the  utilisation  of  all  condensed  steam 
and  hot  water,  and  the  adoption  of  some  efficient  process 
'or  softening  any  hard  water  which  must  be  employed  in 

dition. 

All  these  operations  are  controlled  by  simple  methods  of 
:hemical  analysis.  The  theoretical  value  of  a  given  coal 
ripply  having  been  found  by  analysis,  and  expressed  in 
irms  of  the  heat  units  available,  it  should  be  possible  to 


182  WOOD   PULP  AND  ITS  USES 

determine  what  proportion  has  been  expended  in  useful 
work,  the  particular  stage  in  the  manufacture  of  the  paper 
at  which  each  proportion  has  been  utilised,  and  finally  what 
amount  has  been  wasted.  Questions  of  this  kind  are  of 
great  importance,  and  involve  measurements  of  many  factors. 

Cltcmicals. — From  what  has  been  said  as  to  the  nature 
of  the  operations  involved  in  the  manufacture  of  the  modern 
newspaper,  it  is  evident  that  the  number  of  chemicals 
properly  so  called  is  not  very  large.  Amongst  them  will 
be  found  rosin  and  alkali  used  for  sizing,  or  some  form  of 
prepared  size ;  china  clay  used  as  a  loading ;  lime  for 
the  water-softening  process  ;  alum  and  sundry  colour- 
ing matters  and  pigments  ;  acid  and  bleaching  powder ; 
starch,  etc. 

Oils  and  greases  required  for  lubricating  purposes,  and 
other  supplies  connected  with  economical  power,  also  need 
attention  at  the  hands  of  the  analyst. 

Wood  Pulp. — The  exact  control  of  the  supplies  of  pulp 
is  an  important  part  of  the  duty  of  the  mill  chemist.  The 
determination  of  the  air-dry  weight  of  every  consignment 
of  pulp  is  sometimes  regarded  as  a  mechanical  and  simple 
task,  but  it  is  one  of  considerable  responsibility.  All  pulps, 
whether  delivered  in  a  dry  state  or  in  the  moist  condition, 
require  to  be  tested  for  moisture. 

Chemical  pulps  are  tested  regularly  for  quality,  particu- 
larly as  to  their  behaviour  with  bleach.  Some  pulps  are 
very  difficult  to  bleach,  and  consume  a  large  amount  of 
bleaching  powder.  In  many  cases  where  a  white  pulp  is 
required  a  ready  bleached  pulp  is  used,  but  this  plan  is  not 
economical  since  it  is  cheaper  to  treat  the  pulp  at  the 
paper  mill  than  to  buy  the  material  already  bleached. 


NEWS  AND  PRINTINGS  183 

Mechanical  pulps  vary  in  quality  and  freedom  from  coarse 
fibre.  The  differences  in  bulking  qualities  are  very  marked 
and  may  be  measured  in  the  laboratory  on  small  samples 
readily. 

Paper. — The  examination  of  the  finished  paper  from  the 
machines  in  regard  to  its  physical  properties  of  strength, 
bulk,  finish  and  sizing  is  a  matter  of  routine  in  a  well- 
ordered  mill.  The  testing  of  contract  samples  in  respect 
of  actual  composition  to  determine  the  percentage  of  load- 
ing, the  proportions  of  mechanical  and  chemical  pulps 
present  and  the  existence  of  other  fibres,  as  well  as  the 
usual  physical  tests  mentioned,  is  a  necessity  when  making 
papers  to  sample. 

There  are  many  items  in  manufacture  which  call  for  the 
exercise  of  careful  and  painstaking  research  on  the  part  of 
the  chemist,  and  when  these  technical  questions  are  studied 
exhaustively  by  him  under  the  needful  encouragement  of 
the  authorities,  the  information  gradually  accumulated  is  of 
the  greatest  value.  The  systematic  correlation  of  modifi- 
cations in  manufacture,  with  the  improvements  in  the 
finished  paper  by  proper  classified  records  which  can  always 
be  referred  to,  is  perhaps  one  of  the  most  important  points, 
but  one  which  is  almost  neglected  in  the  average  mill. 

IMPROVEMENTS  IN  THE  MANUFACTURE  OF  CHEAP  NEWSPAPER. 

During  the  last  twenty-five  years  great  progress  has  been 
made  in  the  production  of  common  paper  from  wood  pulps. 
The  contrast  between  the  old  and  new  methods  is  best 
illustrated  by  reference  to  the  output  of  a  machine. 

"When  wood  pulp  was  first  used  there  were  few  machines 


184  WOOD  PULP  AND  ITS  USES 

capable  of  making  a  sheet  of  paper  more  than  120  inches 
wide  at  a  speed  of  200  to  250  feet  per  minute,  with  an 
average  production  of  50  tons  per  week.  To-day  the 
modern  machine  will  produce  a  sheet  of  paper  170  inches 
wide  at  a  speed  of  500  feet  per  minute,  with  an  output  of 
nearly  45  tons  per  day. 

Preparation  of  the  Beaten  Pulp. — The  proper  proportions 
of  mechanical  and  chemical  pulp  are  first  disintegrated  by 
treatment  in  large  potchers  or  special  machinery,  being 
mixed  with  a  suitable  quantity  of  water,  or  generally  with 
waste  waters  from  the  paper  machine.  The  mixture  is  then 
transferred  to  a  beating  engine  capable  of  holding  sufficient 
wet  material  to  produce  one  ton  or  more  of  dry  paper,  and 
beaten  for  about  thirty  or  forty  minutes.  This  is  a  process 
far  removed  from  that  which  obtains  in  the  treatment  of 
rag,  when  the  beating  engine  giving  the  best  results  is  only 
capable  of  holding  wet  stuff  equivalent  to  1  to  2  cwt.  of  dry 
pulp,  and  the  operation  is  only  completed  after  eight  or 
nine  hours. 

To  the  mixture  in  the  engine  about  10  per  cent,  of  china 
clay  calculated  on  the  dry  weight  of  pulp  is  added.  Ptosin 
size  to  the  extent  of  1  or  2  per  cent,  is  then  thoroughly 
incorporated,  and  alum  added  to  precipitate  the  size  which 
adheres  to  the  fibres.  The  pulp  is  suitably  dyed  to  the 
desired  colour  by  means  of  pigments  or  soluble  aniline 
colours. 

The  subject  of  the  beating  of  pulp  is  one  of  great  technical 
importance,  since  the  quality  and  characteristics  of  a  paper 
are  easily  altered  by  modifications  in  the  process  of  beating. 
In  an  elementary  treatise  of  this  kind  it  is  impossible  to 
enter  fully  into  the  question,  and  only  a  brief  indication 


NEWS  AND  PRINTINGS 


185 


can  be  given  of  the  variations  which  are  obtained  as  a  matter 
of  daily  routine. 

The  main  object  of  the  beating  process  is  the  proper 
isolation  and  reduction  of  the  individual  fibres  after  the  raw 
material  has  been  sufficiently  boiled  and  bleached.  There 


FIG.    22.— The  "Hollander"  Beating  Engine. 

are  many  types  of  machines  available  for  the  purpose,  but 
all  constructed  on  the  same  principle,  namely,  the  circu- 
lation of  the  mass  of  pulp  and  water  in  a  narrow  trough 
provided  with  a  revolving  beater  roll  which,  as  it  rotates, 
acts  upon  the  mass  drawn  between  the  knives  of  the  roll 
and  a  set  of  knives  fixed  on  the  bottom  of  the  trough. 
The  general  construction  of  an  ordinary  "  Hollander " 


186  WOOD   PULP  AND  ITS  USES 

beater  is  shown  in  the  diagram.  The  engine  consists  of  an 
oval-shaped  vessel  divided  into  two  channels  by  a  "mid- 
feather  "  or  partition  fixed  along  the  centre  of  the  vessel, 
but  not  extending  completely  to  the  ends.  In  this  way  the 
oval  vessel  is  divided  into  two  channels.  An  adjustable 
beater  roll,  which  is  a  solid  cylindrical  drum  fitted  with 
knives  projecting  from  its  surface,  rotates  in  one  of  the 
channels  and  revolves  above  a  set  of  knives  projecting  from 
the  bottom  of  the  trough.  The  engine  is  filled  with  the  re- 
quired amount  of  pulp  and  water,  and  by  the  rapid  rotation 
of  the  beater  roll  the  mixture  is  constantly  circulated  round 
the  troughs  of  the  engine  and  passes  continuously  between 
the  knives  on  the  beater  roll  and  those  which  are  stationary. 
The  fibres  are  thus  completely  separated  and  gradually 
reduced. 

The  varied  effects  produced  in  beating  wood  pulps  may 
be  illustrated  by  one  or  two  examples.  Thus,  if  soda  pulp 
is  beaten  quickly  with  sharp  knives,  the  beater  roll  being 
close  down  on  to  the  stationary  knives,  then  a  soft  spongy 
paper  resembling  blottings  is  produced.  If  on  the  other 
hand,  a  strong  sulphite  pulp  is  beaten  slowly  for  a  long 
time — eight  or  nine  hours — the  knives  being  blunt,  and  the 
beater  roll  being  lowered  gradually  during  the  process,  then 
a  close  dense  sheet  of  paper,  strong  and  resembling 
parchment,  is  obtained.  In  the  latter  case  the  curious 
assimilation  of  water  by  the  fibre  takes  place,  with  a 
production  of  an  imitation  parchment  paper. 

Probably  the  beating  operation  is  the  most  important  in 
the  various  stages  of  the  manufacture  of  paper,  on  account 
of  the  great  variations  which  are  possible  by  altering  the 
conditions  under  which  the  pulp  is  beaten. 


NEWS  AND  PRINTINGS  187 

It  is  customary  in  mills  where  the  ordinary  type  of 
"  Hollander  "  is  used  to  pass  the  beaten  stuff  through  a 
refiner,  whereby  the  fibres,  which  are  more  or  less  inter- 
locked by  the  beating,  are  brushed  out.  The  types  of 
refiners  mostly  used  in  this  country  are  the  "  Marshall " 
and  the  "  Jordan." 

The  Fourdrinier  Paper  Machine. — The  pulp  after  beating 
is  ready  for  conversion  into  paper.  It  is  discharged  from 
the  beating  or  refining  engines  into  large  reservoirs  or  stuff 
chests,  of  which  there  are  two  to  each  paper  machine.  The 
contents  of  one  chest  are  supplied  to  the  machine  while 
the  second  is  being  filled  from  the  beaters,  so  that  the  pulp 
is  uniform  and  ensures  the  manufacture  of  a  regular  sheet 
of  even  weight  and  thickness. 

The  pulp  flows  through  a  number  of  strainers  which 
serve  to  retain  any  coarse  pieces  of  pulp  and  other  impurities. 
For  the  fast-running  news  machine  the  strainer  is  a  hollow 
circular  drum,  the  shell  of  which  consists  of  a  series  of 
curved  brass  plates  bolted  together,  each  scored  with  fine 
slits.  The  drums  revolve  slowly  and  are  kept  in  a  state  of 
violent  agitation,  so  that  the  fine  pulp  passes  through  the 
slits  and  the  coarse  material  is  retained.  The  mixture  of 
pulp  and  water  flows  in  a  continuous  stream  on  to  the 
surface  of  an  endless  "  wire."  This  consists  of  a  wide  band 
of  wire  gauze  stretched  horizontally  over  two  rolls,  known 
technically  as  the  "  breast  roll"  and  "couch  roll."  The 
stream  of  pulp  is  carried  forward  at  a  rapid  pace,  the  water 
finding  its  way  through  the  meshes  of  the  wire,  and  the 
fibres  settle  down  on  the  surface  of  the  wire  cloth  interlacing 
or  "  felting "  with  one  another.  Further  quantities  of 
water  are  removed  from  the  pulp  by  vacuum  strainers  or 


188  WOOD  PULP  AND   ITS  USES 

boxes  fixed  under  the  wire  near  the  couch  roll,  and  the 
"  web"  of  paper  then  passes  between  the  couch  rolls  which 
compress  the  fibres,  remove  a  certain  proportion  of  water, 
and  give  firmness  to  the  sheet  of  wet  paper. 

The  most  recent  innovations  which  have  been  introduced 
to  facilitate  an  increased  output  of  paper  and  at  the  same 
time  an  improvement  in  the  strength  of  the  sheet,  have  for 
their  object  devices  for  increasing  the  speed  of  the  paper 
machine.  Amongst  these  may  be  mentioned  the  "  Eibel  " 
method  of  manipulating  the  machine  wire.  Under  this 
system  the  wire  cloth  upon  which  the  pulp  flows  is  inclined 
at  a  considerable  angle  from  the  breast  roll  to  the  couch 
roll  so  that  the  material  flows  downhill,  so  to  speak.  By 
this  simple  device  it  is  possible  to  obtain  a  rapid  flow  of  a 
very  dilute  mixture  of  pulp  containing  large  quantities  of 
water,  which  latter  is  easily  removed  owing  to  the  slope  of  the 
wire  cloth.  Another  improvement  is  the  substitution  of  a 
vacuum  couch  roll  in  place  of  the  ordinary  solid  roll  hitherto 
employed,  thus  obviating  the  use  of  a  top  couch  roll.  The 
wet  sheet  of  paper  passes  over  a  large  roll,  part  of  the 
surface  of  which  as  it  revolves  is  submitted  to  the  action 
of  a  powerful  vacuum,  so  that  the  excess  of  water  is 
removed  from  the  wet  sheet  of  paper.  The  fibres  are  felted 
together  and  the  life  of  the  wire  cloth  is  prolonged.  The 
web  leaving  the  couch  rolls  is  drawn  through  two  or  more 
sets  of  press  rolls,  which  serve  to  compress  the  fibres  into 
a  firm  adherent  sheet. 

The  wet  sheet  of  paper  then  passes  over  a  number  of 
drying  cylinders,  which  are  heated  internally  with  steam. 
In  the  earlier  machines  eighteen  to  twenty  such  cylinders 
amply  provided  all  the  drying  surface  necessary,  but  in  the 


NEWS  AND  PEINTINGS  189 

modern  paper  machine  thirty-two  to  thirty-six  cylinders  are 
required  to  dry  the  paper  completely,  owing  to  the  largely 
increased  output. 

The  drying  of  the  paper  is  an  important  item,  because  it 
is  desirable  to  dry  the  paper  as  slowly  as  possible  at  a  com- 
paratively low  temperature.  When  the  number  of  cylinders 
is  limited,  a  much  higher  temperature  is  necessary  to  ensure 
complete  drying  of  the  paper,  but  in  such  case,  while  the 
output  of  finished  paper  can  be  maintained,  the  strength  of 
the  sheet  is  seriously  diminished. 

The  paper  is  afterwards  passed  through  calenders  in  order 
that  a  surface  or  finish  may  be  imparted  to  it.  The 
ordinary  calenders  fixed  at  the  end  of  a  machine  used  for 
the  manufacture  of  news  consist  of  a  number  of  highly 
polished  chilled  rolls,  and  the  paper  in  passing  over  and 
under  these  rolls  is  further  compressed  and  at  the  same 
time  glazed. 

No  further  process  is  necessary  for  ordinary  news,  but  the 
reels  of  paper  produced  at  the  end  of  the  machine  are  re- 
reeled  and  cut  into  the  required  lengths  and  sizes. 


CHAPTER   VII 

WOOD    PULP     BOARDS 

LARGE  quantities  of  mechanical  wood  pulp  are  used  for 
the  manufacture  of  pulp  boards  which  have  many  industrial 
uses  such  as  for  boxes,  packing  cases, .  cards,  calendars, 
advertisement  goods,  picnic  dishes  and  a  variety  of  similar 
articles. 

In  some  cases  the  pulp  is  mixed  with  stronger  fibrous 
material  such  as  jute,  hemp,  and  chemical  wood  pulp, 
particularly  for  boxes  of  high  quality  which  are  required 
to  withstand  rough  usage.  The  heavy  stout  boards 
frequently  used  for  railway  carriage  panels  are  made  from 
the  best  materials  and  by  hand  or  manual  process,  the 
sheets  being  produced  on  moulds  similar  to  those  employed 
in  the  manufacture  of  hand-made  papers. 

The  cheapest  qualities  of  thin  boards,  of  which  an 
ordinary  tram-car  ticket  is  a  typical  example,  are  produced 
on  the  continuous-board  machine,  which  in  general 
construction  resembles  the  ordinary  Fourdrinier  or  paper 
machine. 

For  certain  grades  of  pulp  boards  which  cannot  be  made 
on  the  continuous-board  machine,  on  account  of  the 
thickness,  a  simpler  form  known  as  the  single-board 
machine  is  used. 

The  chief  advantage  of  a  wood-pulp  board  as  contrasted 


WOOD  PULP  BOARDS  191 

with  the  common  strawboard,  which  it  has  superseded  to 
a  large  extent,  are  to  be  found  in  its  more  attractive 
appearance,  its  cleanliness,  and  above  all  its  bulk,  being 
thick  and  of  light  weight.  Moreover  it  has  less  tendency 
to  crack  when  folded  or  bent,  and  when  covered  with 
coloured  paper,  the  colour  does  not  fade  as  frequently 
happens  with  strawboards  which  have  not  been  carefully 
made.  The  traces  of  alkali  often  present  in  common  straw- 
board  produce  a  decided  fading  of  some  aniline  dyes. 

Single-board  Machine. — Mechanical  wood-pulp  boards 
of  any  desired  thickness  are  produced  in  sheets  of  definite 
size  on  this  machine.  It  differs  very  little  from  the  wet 
press  used  in  the  manufacture  of  wood  pulp  itself,  and  only 
a  brief  note  of  its  construction  need  be  given. 

The  pulp  mixed  with  the  requisite  volume  of  water  is 
passed  over  strainers  which  remove  coarse  chips,  and 
pumped  continuously  into  a  large  wooden  vat,  containing  a 
hollow  cylindrical  drum  revolving  at  a  slow  rate. 

The  surface  of  the  drum  consists  of  fine  wire  gauze, 
and  as  the  drum  revolves,  the  pulp  adheres  to  the  surface 
in  a  regular  and  uniform  layer  or  skin,  while  the  water 
passes  freely  through  the  meshes  of  the  wire.  The  layer 
of  pulp  comes  into  contact,  as  it  passes  out  of  the  water, 
with  a  travelling  felt,  and  adhering  to  this,  is  carried  away 
from  the  vat  and  drawn  between  two  heavy  rollers,  which 
squeeze  out  the  excess  moisture.  As  the  thin  sheet  of  pulp 
is  wound  up  on  the  upper  roller,  it  forms  a  sheet  of 
mechanical  pulp  which  gradually  increases  in  thickness, 
and  when  the  desired  thickness  has  been  reached  the 
sheet  is  immediately  cut  away  from  the  roller  and  put 
aside.  The  travelling  felt  passes  round  the  lower  roller 


192  WOOD  PULP  AND  ITS  USES 

and  back  to  the  vat  containing  the  mixture  of  pulp  and 
water. 

The  process  is  continuous,  and  the  sheets  obtained  are 
then  submitted  to  pressure,  thick  felts  being  interposed 
between  the  sheets  of  pulp  so  that  the  water  drains  away 
completely.  The  material  in  this  condition  then  contains 
about  50  per  cent,  of  dry  pulp  and  50  per  cent,  moisture. 
The  sheets  are  dried,  glazed,  and  cut  to  any  required  size, 
the  final  thickness  of  the  boards  being  determined  by  the 
pressure  applied  during  the  process  of  glazing. 

Continuous-board  Machine.  — This  is  a  combination  of 
the  single-board  machine  and  the  ordinary  paper-making 
machine,  and  is  used  for  making  "  duplex  "  and  "  triplex  " 
papers.  The  beaten  pulp  is  formed  into  thin  sheets  in 
two  or  more  vats,  and  these  sheets  are  brought  together 
between  rollers  so  as  to  produce  one  sheet  of  the  required 
thickness.  The  board  then  passes  over  a  large  number  of . 
steam-heated  cylinders,  and  completely  dried.  The  dry 
board  is  also  glazed  and  finished  by  calenders  fixed  at  the 
end  of  the  machine,  and  finally  cut  up  into  sheets. 

No  further  operations  are  necessary,  the  finished  board 
being  manufactured  and  completed  by  the  one  machine, 
the  processes  following  one  another  automatically. 

Machines  of  this  kind  are  frequently  fitted  with  more 
than  two  vats,  and  in  such  cases  some  of  the  vats  are  filled 
with  common  waste  material,  while  two  are  filled  with  a 
high-class  well-bleached  pulp.  In  this  way,  a  good  board 
can  be  produced  cheaply,  consisting  of. a  low-grade  middle, 
covered  on  either  side  with  a  paper  of  good  quality. 
The  colour  of  the  outer  surfaces  of  the  board  can  be 
varied. 


WOOD  PULP  BOARDS  193 

BOX-MAKING. 

The  great  demand  for  boxes  as  a  convenient  substitute 
for  brown  paper  in  the  wrapping  and  packing  up  of  goods 
has  resulted  in  the  creation  of  an  important  industry. 

Raw  Materials. — The  boxes  are  manufactured  from  straw- 
boards,  wood-pulp  boards,  and  "leather"  boards.  The 
nature  of  the  composition  of  the  raw  material  may  generally 
be  gathered  from  the  descriptions  applied,  though  the  term 
"  leather  boards  "  is  somewhat  misleading.  Many  of  the 
so-called  boards  are  made  from  various  kinds  of  specially 
prepared  wood  pulp,  but  in  some  cases  a  small  proportion 
of  leather  clippings  is  incorporated  with  vegetable  fibres  by 
suitable  treatment. 

The  cheap  flimsy  folding  boxes  used  for  wrapping  medicine 
bottles  and  similar  temporary  purposes  are  made  from 
common  board  which  contains  little  more  than  waste 
paper.  The  boards  are  brittle  and  do  not  stand  much 
folding.  The  leather  boards,  on  the  other  hand,  are 
wonderfully  strong  and  tough,  capable  of  being  bent  and 
twisted  into  all  kinds  of  shapes. 

Classification. — The  different  kinds  of  boxes  made  in 
large  quantities  from  the  raw  materials  described  may  be 
classified  as  follows : — 

(1.)  Plain  square-shaped  boxes,  with  corners  pasted,  and 
finished  off  with  plain  or  ornamental  paper. 

(2.)  Square-shaped  boxes,  corners  wire  stitched. 

(3.)  Square-shaped  boxes,  with  metal-edged  corners. 

(4.)  Folding  boxes. 

(5.)  Bound  boxes,  made  up  or  stamped. 

(6.)  Tubes  and  small  cylindrical  cases. 

w.p.  o 


194  WOOD  PULP  AND  ITS  USES 

Plain  Board  Boxes. — The  boards  are  first  cut  into 
convenient  sizes,  on  an  ordinary  cutting  table  worked  by 
hand,  or  in  a  rotary  millboard  cutting  machine  worked  by 
power.  In  the  rotary  machine  a  large  board  can  be  cut 
up  into  a  number  of  strips  of  the  required  length  by  means 
of  circular  knives  fitted  on  to  the  shaft  of  the  machine, 
which  knives  can  be  adjusted  to  any  desired  degree  of 
accuracy.  The  strips  obtained  from  the  cutter  are 
afterwards  reduced  to  the  required  width. 

The  square  pieces  of  board  are  next  scored,  that  is  to 
say,  slight  cuts  are  made  on  the  board  where  the  sides  are 
bent  up  to  form  a  box.  If  the  pieces  of  board  are  not 
scored  in  this  way  they  crack  and  break  when  bent  into  the 
form  of  a  box.  Machines  are  also  employed  in  which  the 
cutting  and  scoring  are  carried  out  simultaneously. 

After  the  boards  have  been  scored  the  corners  are  cut 
out  by  simple  stamping  machines  and  the  box  at  once 
made  up.  The  operator  bends  over  two  edges  of  the  board 
to  form  a  right  angle,  and  places  the  corner  thus  formed  in 
a  stamping  press  which  presses  down  a  small  piece  of 
gummed  paper  of  the  proper  length  round  the  corner 
fastening  the  two  edges  together.  This  operation  is  repeated 
four  times  in  the  making  of  the  boxes.  The  lid  of  the  box 
is  manufactured  in  a  similar  manner,  due  allowance  being 
made  in  the  cutting  of  the  board  in  order  to  obtain  a  well- 
fitting  lid. 

The  boxes  are  left  plain,  or  finished  off  with  printed 
labels  and  ornamental  paper. 

The  covering  of  boxes  with  ornamental  paper  is  a  simple 
process,  the  variations  being  not  so  much  in  the  methods 
employed  as  in  the  materials  used.  Most  of  the  boxes  used 


WOOD  PULP  BOAEDS  195 

by  drapers  are  generally  covered  with  a  flint-glazed  box 
paper,  the  edges  of  the  boxes  being  finished  off  with 
coloured  paper  of  a  similar  character.  The  edges  of  the 
boxes  are  first  covered  with  thin  strips  of  paper  either  by 
hand  or  by  machinery,  the  top  and  sides  of  the  box  being 
afterwards  covered  with  the  white  glazed  paper  in  such 
a  manner  as  to  leave  the  coloured  edges  of  the  box 
exposed. 

Boxes  produced  in  this  way  in  large  quantities  are  finished 
by  means  of  a  "banding"  machine  in  which  a  reel  of 
glazed  paper  is  gummed  on  one  side  and  drawn  on  to  the 
box  which  is  automatically  turned  four  times  by  the 
machine  and  thus  covered. 

Wire-stitched  Boxes. — The  board  used  for  this  class  of 
box  is  cut  into  required  sizes  and  either  scored  or  dented. 
In  the  latter  case  the  board  is  passed  through  a  denting 
machine  which  stamps  a  slight  depression  along  the  line 
which  is  to  form  the  corner  of  the  box. 

The  ends  of  the  board  are  then  slotted  so  that  the  box 
can  be  produced  by  being  turned  up  into  shape  along  the 
lines  formed  by  the  denting  machine.  The  ends  are  then 
fastened  together  by  the  wire  stitching,  in  which  process 
small  pieces  of  wire  are  forced  through  the  ends  of  the 
box  and  clinched. 

Metal-edged  Boxes  are  generally  manufactured  from 
good  material,  such  as  leather  boards,  because  they  are 
intended  for  constant  use.  The  boards  are  usually  grooved 
along  the  bending  line,  either  with  a  square  groove  or  with 
a  deep  V-shaped  groove,  the  latter  being  preferred  as  giving 
the  box  a  neater  finish  at  the  corners  when  completed. 
The  edges  of  the  box  and  the  joints  are  finished  off  with 

o2 


196  WOOD   PULP  AND  ITS  USES 

metal  edging  which  consists  of  a  thin  strip  of  metal  stamped 
out  and  provided  with  sharp  projecting  points.  When  this 
strip  is  forced  into  position  the  projections  pass  through 
the  board  and  being  turned  up  by  the  machine  are  firmly 
clinched.  The  boxes  made  by  this  process  are  very  strong 
and  present  an  attractive  appearance. 

Folding  Cases. — The  cheap  common  cases  used  for 
packing  eggs,  patent  medicines,  and  similar  articles  of 
domestic  use  are  stamped  out  from  thin  cardboard  by 
machinery.  The  general  shape  and  outline  of  the  boxes 
having  been  calculated,  a  metal  forme  or  template  is 
prepared,  by  means  of  which  the  outline  of  the  box  can  be 
stamped  out. 

The  forme  resembles  in  principle  that  used  by  a  printer, 
but  instead  of  raised  type,  strips  of  brass  are  used  and  also 
pieces  of  hardened  steel.  When  the  thin  board  is  placed 
on  the  forme  and  submitted  to  pressure,  the  brass  strips 
indent  the  board  along  the  lines  which  are  to  form  the 
edges  of  the  box,  and  the  steel  knives  cut  out  the  portions 
of  the  board  which  are  not  required.  The  two  edges  which 
overlap  to  form  one  side  of  the  box  are  fastened  together 
with  wire  stitching  or  with  glue.  In  this  condition 
the  box  can  be  folded  flat,  and  when  required  for  use 
it  can  be  opened  up  and  put  together  as  a  box  very 
quickly. 

Postal  Tubes,  etc. — The  many  varieties  of  cylindrical 
boxes  made  for  postal  work,  the  packing  of  gas  mantles, 
phonograph  records,  carbon  paper,  blue  print  and  photo- 
graphic papers,  and  similar  purposes,  are  made  by  covering 
one  side  of  a  board  with  glue  or  some  adhesive  material, 
and  rolling  the  board  up  into  the  form  of  a  tube  on  an 


WOOD   PULP  BOARDS 


197 


iron  roller,  the  diameter  of  which  varies  according  to  the 
size  of  the  bore  of  the  tube. 

For  short  boxes  the  long  tubes  are  cut  up  into  stated 
lengths.  The  caps  for  these  tubes  are  stamped  or  pressed 
out  of  circular  discs  of  flexible  leather  board.  The  whole 
operation  is  exceedingly  simple  and  does  not  require  any 
elaborate  explanation. 


CHAPTEK  VIII 

THE    UTILISATION    OF    WOOD    WASTE 

VARIOUS  methods  of  utilising  wood  refuse  are  in  practice, 
chiefly  based  on  chemical  processes.  The  only  commercial 
application  of  waste  wood  based  on  a  simple  mechanical 
treatment,  and  now  an  extensive  industry,  is  the  manufacture 
of  wood  wool. 

Wood  Wool. — This  is  an  elastic  material  much  used  for 
stuffing  cushions  and  mattresses ;  for  packing  glass,  hard- 
ware, and  fragile  goods  ;  for  filtration,  and  many  other 
purposes  of  diverse  character.  It  is  very  light  and  bulky, 
not  easily  reduced  in  volume  when  wetted,  and  is  thus 
eminently  suited  to  these  and  similar  uses. 

Any  small  odds  and  ends  of  wood  from  carpentering  and 
cabinet  workshops  up  to  14  or  16  inches  long  can  be 
utilised. 

Special  machinery  has  been  devised  for  converting  pieces 
of  wood  of  all  shapes  and  sizes  into  shavings  of  desired 
thickness.  The  pieces  of  wood  are  fed  to  the  machine  by 
hand.  They  are  seized  by  rollers  which  carry  the  wood 
forward  automatically,  bringing  them  under  planing  irons 
and  also  in  contact  with  pointed  knives,  the  thickness  of 
the  shaving  being  determined  by  the  setting  of  the  plane 
irons  and  the  width  of  the  shaving  being  fixed  by  the 
position  of  the  knives  which  produce  cuts  in  the  wood  parallel 


THE  UTILISATION  OF  WOOD  WASTE  199 

to  the  lengh.  One  machine  is  capable  of  producing  6  to  12 
cwt.  of  wood  wool  in  twelve  hours. 

Sawdust. — Large  quantities  of  sawdust  are  produced  in 
many  industries,  and  the  profitable  utilisation  of  this  waste 
material  depends  largely  upon  the  quantity  periodically 
available.  When  the  amount  is  small,  it  is  best  utilised  as 
an  ordinary  packing  material,  but  for  this  there  can  only 
be  a  limited  demand.  Some  idea  of  the  varied  uses  of  saw- 
dust may  be  gathered  from  the  following  brief  description 
of  the  methods  in  use. 

Sawdust  thoroughly  mixed  with  common  rosin  is  con- 
verted into  fire-lighters. 

Mixed  with  highly  concentrated  artificial  manures,  it 
serves  as  a  medium  for  manurial  purposes.  The  sawdust 
itself  has  no  value  as  a  fertiliser,  but  it  has  a  capacity  of 
absorbing  and  retaining  liquids.  Occasionally  the  sawdust 
is  first  converted  into  charcoal. 

Sawdust  has  also  been  employed  as  the  source  of  the 
carbon  in  calcium  carbide.  The  sawdust  is  first  converted 
into  charcoal,  which  is  mixed  with  limestone,  and  the 
mixture  heated  for  several  hours  in  an  electric  furnace. 

In  limited  quantities,  sawdust  is  also  converted  into 
paper  pulp,  but  the  fibre  is  exceedingly  short  and  of  little 
value,  and  it  is  difficult  to  obtain  an  evenly  boiled  material 
owing  to  the  difficulty  of  maintaining  a  proper  circulation  of 
the  caustic  soda,  lye,  or  other  reagent  in  the  digestor. 

Sawdust  is  also  mixed  with  the  concentrated  waste 
liquors  from  the  sulphite  wood-pulp  manufactories,  and 
then  converted  into  briquettes.  These  briquettes  can  be 
used  as  fuel  or  submitted  to  distillation  for  the  manufacture 
of  wood  spirit,  acetic  acid,  and  charcoal. 


200  WOOD  PULP  AND   ITS   USES 

Producer  Gas  from  Wood. — An  interesting  application  of 
the  use  of  waste  wood  is  to  be  found  in  the  generation  of 
"  power  gas."  In  Kiche's  gas-producer  the  wood  is  heated 
in  two  suitable  retorts,  one  of  which  is  used  for  the  distilla- 
tion of  the  wood,  and  the  second  for  the  decomposition  of 
the  gases  obtained  by  the  distillation  of  the  wood  in  the 
first  retort.  The  combustion  is  first  started  in  the  second 
or  reducing  retort.  When  the  heat  has  been  raised  to  the 
proper  extent,  the  distillation  is  commenced  in  the  first 
retort.  The  charcoal  produced  is  withdrawn  periodically 
from  the  bottom  of  the  first  retort  and  thrown  into  the 
reducing  retort.  The  distilled  gases  from  the  first  retort 
are  passed  through  the  heated  charcoal  placed  in  the 
second,  and  subsequently  into  the  gas  holder.  The  gas 
produced  has  a  heating  value  of  about  340  B.T.U.  per  cubic 
foot,  the  quantity  of  gas  per  100  kilos,  of  wood  being  100 
cubic  metres,  or  about  16  cubic  feet  of  gas  per  pound  of 
wood. 

Donkin 1  states  that  about  100  small  plants  of  this  type 
have  been  erected  in  France  and  some  of  the  French  colonies. 
An  interesting  example  is  to  be  found  in  Madagascar,  where 
gas  obtained  in  this  way  is  utilised  in  two  gas  engines  of 
15  and  8  h.p.  respectively  for  the  manufacture  of  artificial 
ice,  the  cost  of  the  motive  power  being  one-third  of  that 
obtained  by  usual  methods. 

Oxalic  Acid. — Sawdust  and  other  forms  of  wood  waste 
yield  oxalic  acid  when  treated  with  caustic  soda.  Forty 
parts  of  sawdust  are  mixed  with  strong  caustic  soda  of 
specific  gravity  1'35,  and  heated  in  shallow  pans  until  the 
temperature  rises  to  220 — 240°  C.  The  product  contains 

1  "  Gas  and  Oil  Engines."     B.  Donkin. 


THE   UTILISATION  OF  WOOD  WASTE 


201 


carbonate  of  soda  and  sodium  oxalate.  This  is  dissolved 
completely  in  boiling  water,  and  the  strength  of  the  solution 
carefully  regulated,  so  that  on  cooling,  the  sodium  oxalate 
crystallises  out.  The  mixture  is  then  treated  in  the  hydro 
extractor  to  remove  the  liquid. 

The  crystals  of  sodium  oxalate  are  dissolved  and  treated 
with  milk  of  lime,  and  thereby  converted  into  calcium 
oxalate.  The  latter  'product  is  precipitated,  separated  from 
the  liquor  by  nitration  or  any  suitable  means,  and  repeatedly 
washed  with  water. 

The  calcium  oxalate  is  then  decomposed  by  treatment  in 
a  lead-lined  vessel,  with  strong  sulphuric  acid,  the  whole 
mixture  being  heated  with  steam,  and  maintained  at  the 
boiling  point  for  some  time.  The  oxalate  is  decomposed, 
giving,  after  treatment  with  the  sulphuric  acid,  a  precipitate 
of  calcium  sulphate  and  a  solution  of  oxalic  acid.  The 
precipitated  calcium  sulphate  is  removed,  and  the  solution 
carefully  evaporated  for  the  production  of  crystallised 
oxalic  acid. 

The  amount  of  oxalic  acid  obtained  may  be  varied 
according  to  the  method  of  heating.  Thus  the  percentage 
yield  is  increased  by  using  potassium  hydrate  as  well  as 
sodium  hydrate,  and  also  by  heating  the  material  in  thin 
layers.  The  yield  of  oxalic  acid  from  various  woods  is  as 
follows : — 


Spruce 
Poplar 
Beech  . 
Oak 


94-7 
93-0 
86-3 
84-4 


202  WOOD   PULP  AND  ITS   USES 

THE  DESTRUCTIVE  DISTILLATION  OF  WOOD. 

When  wood  is  burnt  under  conditions  which  restrict  the 
supply  of  air,  or  heated  in  closed  retorts,  it  passes  through 
a  process  of  destructive  distillation  with  the  production  of 
certain  valuable  commercial  substances. 

The  combustion  of  wood  in  a  confined  space  was  resorted 
to  in  early  days  for  the  manufacture  of  charcoal  simply, 
and  large  quantities  of  this  charcoal  are  produced  even 
to-day  by  the  primitive  method  of  stacking  wood,  covering 
it  with  earth  and  setting  fire  to  the  wood  at  the  bottom  of 
the  pile.  The  only  substance  obtained  was  the  charcoal 
left  when  the  process  was  completed,  but  about  1812  the 
discovery  of  the  presence  of  wood  spirit  and  acetic  acid  in 
the  vapours  given  off,  led  to  a  closer  study  of  the  chemical 
changes  taking  place. 

The  products  of  distillation  are  chiefly  acetic  acid,  wood 
spirit  (methyl  alcohol)  tar,  gases  and  charcoal.  By  slow 
distillation  at  a  low  temperature  a  maximum  yield  of  acetic 
acid  and  tar  is  obtained.  The  gas  given  off  during  the 
operation,  a  mixture  of  carbon  dioxide  and  carbon  mon- 
oxide, is  utilised  by  passing  it  through  the  furnace  employed 
in  heating  the  retorts.  The  carbon  dioxide  is  reduced  to 
monoxide,  a  combustible  gas  which  gives  off  its  available 
heat  in  the  furnace. 

By  rapid  distillation  at  a  high  temperature,  the  volatile 
products  are  decomposed  giving  a  greater  yield  of  gas  and 
a  smaller  proportion  of  acetic  acid. 

The  effect  of  the  method  of  heating  is  shown  in  the 
following  table  taken  from  Fischer's  Chemical  Technology. 
In  the  sloiv  distillation  process,  the  wood  was  heated  slowly 


THE  UTILISATION  OF  WOOD  WASTE 


203 


for  six  hours,  starting  with  cord  retorts,  while  in  the/as£ 
distillation  the  wood  was  placed  at  once  in  heated  retorts 
and  treated  for  three  hours. 


Percentage  yield  of  distillation  products. 

Wood. 

Total 
distillate. 

Tar. 

Wood 
vinegar 
crude. 

%  pure 
acetic 
acid. 

Dry 
charcoal. 

Gases. 

Birch- 

slow  .     . 

51-05 

5-46 

45-59 

5-63 

29-64 

19-71 

fast    . 

42-98 

3-24 

39-74 

4-43 

21-46 

35-56 

Beech  — 

slow  . 

51-65 

5-85 

45-80 

5-21 

26-69 

21-66 

fast    .     . 

44-35 

4-90 

39-45 

3-86 

21-90 

33-75 

Oak- 

slow  . 

48-15 

3-70 

44-45 

4-08 

34-68 

17-17 

fast    . 

45-24 

3-20 

42-04 

3-44 

27-73 

27-03 

Larch  — 

slow  .     . 

51-61 

9-30 

42-31 

2-69 

26-74 

21-65 

fast    .     . 

43-77 

5-58 

38-19 

2-06 

24-06 

32-17 

Spruce  — 

slow  . 

46-92 

5-93 

40-99 

2-30 

34-30 

18-78 

fast    .     . 

46-35 

6-20 

40-15 

1-78 

24-24 

29-41 

In  practice  the  distillation  of  wood  is  carried  out  with 
due  regard  to  the  nature  and  quantity  of  the  desired  products, 
and  the  method  of  treatment  varied  accordingly. 

Steam  Distillation.  —  With  pine  and  woods  rich  in 
turpentine  oils  the  material  previously  reduced  to  the 
condition  of  small  chips  is  heated  by  means  of  steam  in 
closed  vessels  at  a  pressure  of  40  Ibs.,  and  the  oils  distilled 
off  by  the  steam. 

This  process  is  usefully  employed  in  the  pulp  mill,  since 
the  manufacture  of  paper  pulp  from  pine  wood  can  be  con- 
ducted in  such  a  way  as  to  ensure  the  extraction  of  the 
turpentine  from  the  digesters  and  the  subsequent  conversion 


204 


WOOD   PULP  AND   ITS  USES 


of  the  wood  into  pulp.  The  soda  process  of  paper-making 
is  easily  adapted,  for  the  ordinary  steam  pressure  is  sufficient 
to  drive  off  all  the  volatile  oils,  and  most  of  the  resinous 
matters  are  converted  into  soluble  soda  compounds. 

Dry  Destructive  Distillation. — The  products  obtained  from 
different  woods  as  determined  by  the  Bureau  of  Chemistry, 
Washington,  are  shown  in  the  following  table  : — 


Average  yield  per  cord  of  wood  (128  cubic  feet  piled  wood). 

Hard  woods. 

Resinous 
woods. 

Hard  wood 
sawdust. 

Charcoal  (bushels)     . 

45 

30 

30 

Crude   wood    spirit   containing 

acetone  (gallons)    . 

10 

3 

3 

Acetate  of  lime  (Ibs.) 

75 

120 

60 

•Tar  (gallons)      .... 

15 

45 

— 

Wood  oil  (gallons)     . 

— 

45 

— 

Turpentine  (gallons) 

— 

10 

— 

In  the  slow  distillation  process,  a  maximum  yield  of  solid 
product  is  aimed  at,  with  a  minimum  quantity  of  gas. 
Harper  gives  the  results  of  a  test  on  dry  yellow  pine : — 


Yield  per  cord,  air-dry. 

Gallons. 

Ibs. 

% 

Turpentine 

18-64 

134-20 

3-679 

Wood  oil 

11-09 

86-50 

2-371 

Tar. 

96-0 

846-72 

23-216 

Acid 

96-0 

830-49 

22-771 

Cake 



14-74 

•404 

Charcoal  . 



796-00 

21-826 

Yellow  oil  and  pitch 

6-78 

57-02 

1-563 

Gas  and  Loss  . 

— 

881-33 

24-170 

3,647-0 

100-000 

THE  UTILISATION  OF  WOOD  WASTE 


205 


With  the  rapid  distillation  method,  a  maximum  yield  of 
gas  is  obtained,  and  in  this  case  the  process  is  utilised  for 
the  manufacture  of  illuminating  gas  or  for  power  gas.  All 
kinds  of  waste  wood  material  such  as  sawdust  are  turned 
to  good  account  in  this  way. 


CHAPTEE  IX 

TESTING   OF   WOOD    PULP    FOB    MOISTURE 

IN  the  selling  and  buying  of  wood  pulps  the  question  of 
associated  moisture  is  of  obvious  importance,  regulated  by 
convention  and  by  standards,  it  requires  to  be  controlled 
by  actual  tests.  The  mechanical  wood  pulps  are  generally 
shipped  from  the  mills  in  the  form  of  bales  containing 
moist  pulp  on  the  basis  of  50  per  cent,  air-dry  pulp.  The 
chemical  pulps  are  shipped  usually  in  bales  containing  the 
air-dry  pulp. 

Disputes  frequently  arise  as  to  the  exact  air-dry  weight  of 
pulp  received,  the  chemical  pulps  frequently  containing 
moisture  in  excess  of  the  standard,  and  the  mechanical 
pulp  also  containing  a  larger  amount  of  moisture  than  50 
per  cent. 

No  satisfactory  standard  method  has  yet  been  found  for 
the  sampling  and  testing  of  wood  pulp.  When  the  freshly 
made  bales  are  shipped  from  the  pulp  mill  so  that  the 
whole  of  the  sheets  in  the  bale  are  uniform,  then  it  is 
comparatively  easy  to  take  samples  from  the  bale  which 
shall  fairly  represent  the  pulp.  If,  however,  the  distribu- 
tion of  moisture  in  the  bale  has  been  altered  to  any  extent, 
either  by  loss  in  weight  owing  to  the  drying  of  the  outer 
sheets  and  exposed  edges  of  the  bale  during  prolonged 


TESTING   OF  WOOD   PULP  FOE   MOISTURE         207 

storage,  or  on  the  other  hand  if  the  bales  have  become 
much  heavier  by  accidental  wetting  through  rain  or  other 
causes,  then  the  sampling  is  by  no  means  an  easy  matter. 

Frequently  the  water  in  the  bale  freezes,  and  in  conse- 
quence of  this  much  of  the  water  is  drawn  from  the  interior 
of  the  sheets  and  deposits  itself  as  a  layer  of  snow  or  ice 
between  the  sheets  which  lie  upon  one  another  in  the 
bale. 

The  bale  when  opened  falls  apart  most  readily  just  at 
those  points  where  the  surface  of  the  sheet  is  covered  with 
ice,  and  it  is  almost  impossible  under  such  circumstances 
to  take  out  samples  that  shall  fairly  represent  the  whole 
bale.  Even  when  this  ice  has  thawed  out  sufficiently  to 
resume  the  form  of  water,  it  does  not  distribute  itself 
evenly  through  the  pulp  for  a  very  long  period. 

General  Principles. — A  certain  proportion  of  the  bales 
which  form  a  consignment  are  selected  for  the  test. 
Usually  4  per  cent,  of  the  number  of  bales  are  taken,  due 
care  being  exercised  in  the  selection  so  that  the  bales  are 
sound,  in  good  condition,  and  do  not  exhibit  any  serious 
deviations  in  gross  weight. 

The  selected  bales  are  weighed  and  sampled.  The 
samples  as  cut  are  immediately  put  into  bottles,  or  tins, 
which  are  sealed  up  and  taken  to  the  laboratory  where 
they  are  dried  at  a  temperature  of  100°  C.  and  the  percent- 
age of  absolutely  dry  pulp  determined.  The  weight  of 
air-dry  pulp  is  calculated  from  this  figure  on  the  arbitrary 
basis  that  90  parts  of  absolute  dry  pulp  give  100  parts  of 
air-dry  pulp. 

The  analyst  gives  a  certificate  in  accordance  with  the 
following  schedule :— 


20S  WOOD   PULP  AND  ITS   USES 

WOOD  PULP  MOISTURE  CERTIFICATE. 
(Form  adopted  by  the  British  Wood  Pulp  Association.) 
THIS  is  TO  CERTIFY  that  I  have  tested  for  moisture  a 

parcel  of 

Pulp,  said  to  consist  of  bales,  marked 

lying  at 

The  samples  were  drawn  by  me  on 

Bales.     T.     Cwt.     Qrs.     Lbs. 

Total  gross  weight  of  bales  sampled  (intact)     , 
(For  numbers  and  detailed  weights  see  below.') 

Weight  of  Parcels  calculated  from  above  . 
Percentage    of    absolutely  dry  pulp    in    the 

sample         .        .  .     ...    -    •  percent. 

,,  moisture  in  the  sample  .        »  ,, 

„  air-dry  or  moist  pulp  in  the 

parcel  on  the  basis  of 
90=100  (air-dry)    .  •  „ 

45=100  (moist)        .  „ 

„  excess  Moisture,  Fibre  . .  ,, 

T.     Cwt.    Qrs.    Lbs. 

Weight  of  Pulp  to  be  invoiced  .        *,      .,  v 

NUMBEES  AND  DETAILED  WEIGHTS  OF  BALES  SAMPLED. 


Analyst. 

Difficulties  in  Sampling. — In  practice  it  is  found  that  the 
testing  of  wood  pulp  for  moisture  offers  many  difficulties. 
The  uniformity  of  the  moisture  throughout  the  bale  is 
seriously  disturbed  by  the  causes  already  described  so  that 
not  only  is  it  difficult  to  select  really  representative  bales, 
but  the  work  of  cutting  out  samples  is  also  complicated. 

Various  methods  are  employed  for  taking  out  samples  of 
pulp,  and  at  present  there  is  no  standard  method,  although 
attempts  have  been  made  to  establish  a  uniform  system. 


TESTING  OF  WOOD  PULP  FOR  MOISTURE          209 

It  is  scarcely  necessary  to  enter  into  any  prolonged 
discussion  as  to  the  merits  of  the  various  methods  each  of 
which  are  no  doubt  correct  under  certain  conditions.  With 
pulp  that  has  not  been  in  stock  more  than  three  or  four 
weeks  any  reasonable  system  would  give  correct  results,  but 
the  difficulty  is  to  find  a  system  which  would  give  correct 
results  on  freshly  made  pulp  and  exactly  the  same  results 
on  the  pulp  after  having  been  in  stock  several  months. 

Probably  the  system  which  finds  general  favour  is  that 
known  as  the  " wedge"  method,  in  which  it  is  assumed 
that  a  wedge  having  its  apex  at  the  centre  of  the  sheet  of 
pulp  and  a  base  of  any  desired  width  at  the  outer  edge  of 
the  sheet  of  pulp  represents  the  sheet  itself,  taking  the 
correct  proportions  of  the  inner  and  outer  sections  of  the 
sheet.  This  may  be  explained  by  reference  to  the  diagram 
in  Fig.  23. 

Let  ABCD  represent  a  sheet  of  air-dry  pulp  of  uniform 
thickness,  measuring  24  inches  by  18  inches,  and  divided 
into  four  equal  parts — E,  the  inside  portion  ;  H,  the  outer 
portion  ;  and  F,  G,  intermediate  portions,  thus : — 

Square  inches. 

Area   E  12"  x  9"  =  108*0 

Areas  E,  F  =  16-975"  X  12*73"    =  216*0 

Areas  E,  F,  G         =  20'785"  X  15*585"  =  324'0 

Areas  E,  F,  G,  H  =         24"  x  18"         =  432-0 

Square  inches. 

E  =  108 

F  =  108 

G  =  108 

H=  108 

Total  =        ~ 
W.P. 


WOOD  PULP  AND   ITS  USES 


24 


12" 


<--£  --> 

PIG.  23. 


FIG.  23A. 


TESTING  OF  WOOD  PULP  FOE  MOISTURE          211 

The  dimensions  of  the  various  rectangles  are  all  propor- 
tional, that  is,  the  ratio  of  the  length  to  the  breadth  is  the 
same  in  all  cases,  viz.,  24  to  18. 

A  sample  from  the  sheet  which  shall  represent  the  whole 
is  obtained  by  taking  equal  areas  from  each  of  the  pieces 
E,  F,  G,  H  ;  but  in  practical  testing  such  a  course  is 
impossible,  as  it  would  necessitate  marking  the  exact 
position  of  the  "  lines  of  separation "  before  the  small 
pieces  of  equal  area  could  be  cut.  Another  alternative 
would  be  to  cut  a  quarter  sheet  from  the  whole — an  equally 
impracticable  scheme.  But  a  wedge  gives  four  equal-sized 
pieces  from  the  four  areas  E,  F,  G,  H. 

Let  such  a  wedge  having  a  base  of,  say,  2  inches,  be 
drawn  as  shown  in  Fig.  23.  Let  Fig.  23A  represent  the 
wedge  on  an  enlarged  scale,  consisting  of  the  four  areas  e,f, 
g,  h.  The  area  of  the  whole  sheet  is  24  inches  by  18  inches, 
or  432  square  inches,  and  the  areas  of  the  wedge  is  that  of  a 
triangle  whose  height  is  9  inches  and  whose  base  is  2  inches. 

The  wedge  contains  a  series  of  triangles,  viz.,  (1)  the 
triangle  e  :  (2)  triangle  consisting  of  pieces  ef\  (3)  triangle 
consisting  of  e,f,  g  ;  (4)  triangle  consisting  of  pieces  efgh. 
By  calculating  the  area  of  each  triangle  the  exact  size  of  the 
separate  pieces  e,f,  g,  h  is  found. 

The  height  and  base  of  each  triangle  is  easily  cal- 
culated : — 

(1)        Base  of  triangle  e  Height  of  triangle  ef 

Base  of  triangle  (efgh)  Height  of  triangle  (efgh) 

Base  of  e      45 

=  —  giving  1*0  inches. 

2  9 

p  2 


212  WOOD   PULP  AND  ITS  USES 

(2)       Base  of  triangle  ef  Height  of  triangle  cf 


Base  of  triangle  (efgli)  Height  of  triangle  (efgh) 

Base  of  ef        6'365 

= giving  T4144  inches. 

2  9 

The  other  triangles  are  treated  in  a  similar  manner  and 
the  areas  readily  calculated. 

(Area  of  a  triangle  =  \  base  X  height.) 

Square  Inches. 

Triangle  hgfe  has  area  j  (2  X  9)  =9 

gfe          „        i  (1-7315  X  7'7925  =  6'75 
fe  „         i  (1-4144  X  6-365)    =  4'50 


„         c  „ 


(1  X  4-5)  =  2-25 


From  the  above  figures  the  areas  of  the  pieces  e,  J,  g,  h, 

are  :  — 

Square  Inches. 
e  =  2-25 
/  =  2-25 
g  =  2-25 
h  =  2-25 

Hence  any  sized  wedge  contains  what  the  pulp  maker 
defines  as  correct  proportions  of  "inside  and  outside  pulp," 
at  any  rate  mathematically. 

Absolute  Dry  and  Air-dry  Pulp.  —  The  exact  air-dry  weight 
of  pulp  is  calculated  on  the  basis  that  100  parts  of  air-dry 
pulp  consists  of  90  parts  absolute  dry  pulp  and  10  parts 
of  natural  moisture.  This  is  an  arbitrary  figure  based 
on  the  assumption  that  air-dry  pulp  contains  10  per  cent. 
of  natural  moisture.  As  a  matter  of  fact  the  air-dry 
weight  of  pulp  varies  according  to  the  conditions  of  the 


TESTING  OF  WOOD   PULP  FOE  M01STUEE 


213 


atmosphere,  but   for  trade  purposes  the  arbitrary  figure 
selected  is  convenient. 

In  1896  Sindall  made  some  experiments  with  a  view 
of  determining  the  influence  of  the  atmospheric  moisture 
upon  the  weight  of  wood  pulp.  Numerous  samples  were 
exposed  to  ordinary  atmospheric  conditions  for  nearly  two 
years,  the  samples  of  pulp  being  weighed  two  or  three  times 
a  week  and  the  relative  humidity  of  the  air  being  also  noted. 
The  following  table  was  compiled  as  the  result  of  these 
experiments,  showing  the  air-dry  weight  of  the  exposed 
pulps,  the  actual  absolute  dry  weight  of  pulp  being  88  parts 
in  each  case. 

SHOWING  THE  VARIATION  OF  THE  WEIGHT  OF  PULP  DUE  TO 
MOISTURE  IN  THE  AIR. 


Relative  Humidity. 
H. 

Mechanical  Pulp. 

Sulphate  and  Soda 
Pulp. 

Sulphite  Pulp. 

Average. 

Average. 

Average. 

51-4 

99-03 

95-98 

96-53 

60-00 

100-04 

96-42 

96-85 

65-30 

100-42 

96-91 

97-45 

77-20 

102-24 

98-60 

99-30 

80-13 

102-41 

98-21 

99-30 

82-10 

102-78 

98-41 

99-74 

82-70 

102-58 

98-70 

99-69 

82-90 

102-84 

98-78 

99-80 

83-20 

103-55 

98-95 

100-50 

83-90 

103-17 

98-98 

100-63 

85-10 

103-81 

99-42 

100-60 

86-60 

105-13 

100-41 

101-63 

87-50 

104-55 

99-92 

101-04 

88-24 

104-64 

100-23 

100-93 

89-10 

104-63 

100-02 

101-14 

90-00 

105-40 

100-70 

101-90 

93-00 

106-82 

102-40 

103-76 

The   exact   relation  between   the   humidity   of   the   air 
and    the    air- dry    weight    of    wood    pulp    as    determined 


214 


WOOD  PULP  AND  ITS  USES 


by  these  experiments  may  be  expressed  in  the   following 
way  :— 

If  the  numbers  representing  humidity  form  a  series  in 
arithmetical  progression,  then  the  weight  of  wood  pulp 
corresponding  to  those  numbers  produces  a  series  of  figures 
in  geometrical  progression,  thus  : — 

Humidity  =  H,  H  +  d,  H  +  2d,  H  +  3d,  H  +  4d, 
Weight  =  W,  Wr,  Wr2,  Wr3,  Wr4, 

Where  d  =  5,  r  =  1/28. 

If  the  results  given  in  the  table  are  plotted  in  the  form 
of  a  curve,  it  is  possible  to  correct  the  errors  of  observation 
and  determine  the  air-dry  weight  of  pulp  for  every  5  degrees 
difference  in  the  humidity  of  the  air. 

SHOWING    TEE  VARIATION   OF   THE   WEIGHT   OF  PULP   FOR  EACH 
5  DEGREES  INCREASE  IN  THE  HUMIDITY  OF  THE  AlR. 


Air-dry  Weight  of  Pulp. 

Relative 

Average 

Humidity. 

difference 

Constant  r. 

H. 

Mechanical. 

Sulphate  and 
Soda. 

Sulphite. 

for  5°  H. 

50 

98-95 

95-90 

96-35 

0-26 

55 

99-30 

96-10 

96-60 

0-33 

1-25 

60 

99-70 

96-35 

96-95 

0-42 

1-27 

65 

100-20 

96-65 

97-40 

0-52 

1-24 

70 

100-80 

97-05 

97-95 

0-68 

1-30 

75 

101-60 

97-60 

98-65 

0-82 

1-30 

80 

102-50 

98-30 

99-50 

1-13 

1-35 

85 

103-75 

99-35 

100-60 

1-52 

1-34 

90 

105-25 

100-80 

102-20 

— 

— 

Mean=l-28 

CHAPTEK   X 

WOOD   PULP   AND    THE    TEXTILE    INDUSTKIES 

THE  celluloses  and  compound  celluloses  are  produced  in 
definite  and  characteristic  structural  forms,  and  only  in  such 
form.  By  chemical  processes  such  as  described  in  Chapter  II., 
we  may  convert  the  original  structural  celluloses  into  its 
amorphous  or  structureless  forms  by  way  of  solutions  of 
derivative  compounds.  It  is  clear,  however,  that  questions 
of  form  and  dimensions  underlie  every  technical  problem 
involved  in  the  applications  of  cellulose. 

The  following  are  the  dimensions  of  the  more  important 
celluloses,  considered  as  ultimate  fibres. 

Length  of  Fibre.  Diameter. 

( Cotton  20—40     mm. 

..,  \Flax  25—30        „    0-015— 0-037 

Fine  textiles.         j  Rhea  60-200          0-030—0-070 

VHemp  15—25 

/Jute  1-5—4-0 

Coarse  textiles       \  Sisal  1-5—6-0 

and  Rope-making.  \  Phormium  5*0 — 15-0 

V  Pinewood  (Tracheids)  1-0—20-0 

Paper-making  Esparto  0-5— 3'0 


0-016—0-050 
0-020—0-025 
0-015—0-026 
0-010—0-020 
0-015—0-020 
0-010—0-018 


It  is  somewhat  remarkable  that  the  most  important 
cellulose,  cotton,  occurs  and  is  industrially  worked  as  an 
ultimate  fibre  or  structural  unit. 

Incidentally,  it  is  worthy  of  mention  that  cotton  is  a  seed 
hair,  and  in  physiological  function  therefore,  being  con- 
cerned with  a  usually  perishable  tissue,  it  is  not  a  priori 


216  WOOD  PULP  AND  ITS  USES 

associated  with  permanence.  On  the  same  grounds  and 
for  the  contrary  reason  we  should  expect  to  find  in  the 
wood  substances  which  have  long  continuing  or  perennial 
functions,  a  chemical  constitution  implying  superior 
stability.  The  paradox,  however,  holds  that  cotton  is  our 
type  of  chemically  balanced  cellulose  and  of  a  higher  order 
of  stability  than  the  wood  celluloses. 

To  complete  this  point  we  must  refer  the  reader  to  the 
previous  section,  which  deals  with  the  conditions  of  per- 
manence of  the  ligno-celluloses  which  are  natural  compound 
forms.  We  have  to  remember  also  that  a  wood  cellulose  is 
a  residue  always  of  chemical  processes. 

As  regards  structure  the  woods  are  highly  complex, 
whereas  most  of  the  textile  fibres  mentioned  above  are 
either  bast  fibres  (bundles)  or  fibre  vascular  bundles.  In 
the  former  case,  as  in  flax,  rhea,  and  hemp,  the  bundle  is 
simple.  It  is  more  complex  in  the  case  of  jute  (see 
Chap.  I.),  and  still  more  complex  in  the  fibre  vascular 
bundles  of  monocotyledons. 

Esparto  is  a  heterogeneous  aggregate  as  in  the  case  of 
the  woods. 

In  the  mere  complex  structures  the  celluloses  are 
associated  with  various  chemical  groups  (compound  cellu- 
loses), which  are  attacked  and  removed  by  the  various  treat- 
ments of  hydrolysis  and  oxidation  by  which  the  celluloses 
are  isolated.  For  our  present  purpose  we  are  concerned 
only  with  the  celluloses  in  the  form  of  ultimate  fibres. 
These  are  the  unit  elements  of  structure  of  the  yarns  and 
threads  which  are  the  basis  of  textile  fabrics.  The 
mechanical  properties  of  these,  as  well  as  the  processes  by 
which  they  are  mechanically  prepared  and  ultimately  spun, 


WOOD  PULP  AND  THE  TEXTILE  INDUSTKIES      217 

are  obviously  determined  by  their  simpler  elements  of  form- 
that  is,  their  dimensions. 

The  mechanical  principles  involved  in  the  production  of 
fine  textile  yarns  from  these  discontinuous  units,  are  first, 
the  reduction  of  these  to  a  common  untwisted  sliver,  in 
which  they  are  parallelised ;  secondly,  the  drawing  and 
twisting  of  the  fibres  composing  the  sliver  in  continuous 
length. 

The  tensile  properties  of  the  resulting  yarn  depend  mainly 
upon  the  twist,  partly  upon  the  adhesion  of  the  more  or  less 
closely-spun  fibres. 

There  are  numerous  variations  of  the  process,  such  as  the 
wet  spinning  applied  to  bast  fibres  and  notably  flax,  the 
passage  of  the  sliver  through  a  bath  of  warm  water  facili- 
tating the  ultimate  subdivision  of  the  bundles  of  fibres 
in  the  final  drawing  and  twisting  operation.  In  the 
coarser  textiles,  such  as  jute,  it  is  evident  that  the  spinning 
unit  is  an  aggregate  or  bundle  of  the  ultimate  fibres,  which 
are  too  short  (2  to  3  mm.)  to  admit  of  manipulation. 

They  are  worked  in  lengths,  which  have  reference  to  the 
conditions  of  the  machinery,  most  convenient  for  preparing, 
drawing,  and  twisting.  But  it  must  be  borne  in  mind  as  a 
fundamental  technical  fact  that  the  ultimate  properties  of 
the  yarn  are  conditioned  primarily  by  the  length  of  the 
ultimate  fibre.  This  will  be  evident  from  the  table 
(p.  232),  giving  the  relative  strengths  of  textile  yarns  in 
terms  of  actual  tenacity  and  apparent  elasticity  (extensi- 
bility). We  have  added  to  the  list  the  new  products 
known  as  artificial  silk,  or  lustracellulose.  This  being  pre- 
pared from  structureless  solutions  of  cellulose  derivatives 
may  be  considered  as  structureless.  In  this  sense  they 


218  WOOD  PULP  AND  ITS   USES 

resemble  the  true  silks  which  are  produced  in  solution  in 
the  glands  of  the  silkworm  and  extruded  into  the  atmo- 
sphere, the  worm  performing  the  mechanical  operation 
of  drawing  and  laying  the  threads  in  the  specialised  form 
of  cocoon. 

The  structureless  cellulose,  in  the  form  of  a  thread  of 
regular  dimension,  presents  to  us  a  case  of  mechanical  pro- 
perties of  a  substance  independently  of  the  grosser  structural 
details  which  characterise  the  natural  cellulose  fibres,  and 
it  will  be  seen  that  cellulose  admits  of  very  severe  treat- 
ment in  passing  through  a  cycle  of  operations  and  reverting 
to  an  amorphous  substance  which  retains  much  of  the 
structural  properties  of  the  original. 

Reverting  now  to  the  fibrous  celluloses,  there  are  certain 
features  common  to  the  paper-making  and  the  textile 
industries.  Thus,  a  web  of  paper  and  a  textile  yarn 
may  be  made  from  the  same  raw  material,  and,  more- 
over, have  the  common  characteristic  of  an  agglomerate 
of  discontinuous  fibrous  elements  produced  in  continuous 
length.  The  strength  or  cohesion  of  the  two  fabrics  depends 
in  the  first  place  upon  the  surface  adhesion  of  the  fibrous 
units,  but  in  the  case  of  the  textile  yarn  this  is  a  much  less 
important  factor  than  the  "  twist "  communicated  by  the 
spinning  process.  On  the  other  hand  the  paper  web,  though 
devoid  of  twist,  presents  certain  characteristics  in  the 
opposition  and  adhesion  of  its  structural  units,  which  makes 
it  a  more  coherent  agglomerate  than  the  yarn.  Generally 
this  is  referable  to  the  wet  processes  of  the  paper-maker, 
which  brings  the  colloidal  fibre  substance  into  a  condition 
of  hydration  or  gelatinisation,  in  which  a  more  intimate 
adhesive  contact  of  the  fibre  surfaces  is  determined.  The 


WOOD   PULP  AND  THE  TEXTILE  INDUSTRIES      219 

cohesion  is  augmented  by  the  pressure  to  which  the  web  is 
subjected  while  still  in  the  wet  state  and  the  union  of  the 
fibre  surfaces  is  finally  cemented  by  the  drying  or  dehydra- 
tion of  the  web.  Conversely,  when  re-wetted  a  paper  is 
brought  back  into  approximately  the  condition  of  the  web 
as  first  put  together  and  its  cohesion  in  this  state  or 
wet-strength,  is  only  a  fraction  of  that  of  the  paper. 
The  cohesion  of  a  textile  yarn,  on  the  other  hand,  is 
only  slightly  affected  by  wetting,  and  the  effect  indeed 
is  not  necessarily  in  the  direction  of  diminishing  tensile 
strength. 

The  main  point  of  contrast  between  these  great  divisions 
of  manufactures  devoted  to  the  industrial  utilisation  of  the 
vegetable  fibres,  is  the  length  of  the  unit  fibre,  or  fraction 
of  fibre,  in  the  final  state  of  preparation  of  the  raw  fibrous 
material.  Generally,  we  may  say  that  the  limit  of  economic 
handling  in  the  textile  industry  is  reached  with  a  length  of 
fibre  of  3 — 5  mm.  This  inferior  limit  expresses,  on  the 
other  hand,  the  outside  limit  imposed  upon  the  paper- 
maker  for  the  satisfactory  working  of  his  Wet  web  upon 
the  wire  cloth  of  the  machine  or  hand  mould,  and  for  the 
majority  of  papers  a  length  of  1 — 2  mm.  is  a  working 
optimum. 

This  corresponds  with  an  obvious  complementary  rela- 
tionship of  the  two  industries,  and  the  paper-maker,  up  to 
fifty  years  ago,  was  practically  limited,  as  to  raw  material, 
to  the  wastes  of  the  textile  industries. 

In  later  times  there  have  been  notable  advances  in  the 
method  of  working  up  short  fibre  wastes  by  the  spinner's 
dry  methods,  "  ginning  process,"  and,  by  special  modifica- 
tions of  teasing  or  carding  machines,  the  utilisation  of 


220  WOOD  PULP  AND  ITS  USES 

these  short  fibres  has  been  carried  to  extreme  limits.  As 
a  question  of  cost  of  production  it  is  found,  however,  that 
the  paper-making  process  has  considerable  advantage.  The 
problem  then  arises  of  converting  the  continuous  length  of 
paper  into  a  textile  yarn,  with  the  associated  question  of 
the  actual  utility  of  the  product.  The  elements  of  the 
problem  are  these  : — 

(1)  The  subdivision  of  the  web  of  paper  into  strips  of 
suitable  dimensions. 

(2)  The   rolling   of   these   strips    continuously  into  the 
cylindrical  form. 

(3)  Subjecting  the  cylindrical  length  of  paper  "  felt "  to 
a  twisting  operation  so  as  to  increase  its  tensile  strength 
to  a  maximum. 

Having  by  these  processes  appreciated  to  a  maximum 
the  tensile  qualities  of  the  fibrous  agglomerate,  we  still 
have  to  reckon  with  the  intrinsic  limitations  of  quality, 
due  to  shortness  of  fibre,  on  the  one  hand,  and  the  fact 
that  when  wetted  the  product  loses  its  cohesion. 

This  is  a  general  and  somewhat  " theoretical"  expose  of 
the  technical  basis  of  an  industrial  movement  which  has 
been  in  progress  since  1891,  toward  the  utilisation  of  paper 
in  the  form  of  a  textile.  It  may  be  noted  that  this  move- 
ment, though  quite  new  to  Europe,  is  based  upon  old- 
world  practice,  for  the  Japanese  have  for  centuries  used 
paper  as  a  basis  of  string  or  twine,  twisting  paper  strips  of 
convenient  width  into  the  cylindrical  form,  and  also  piecing 
successive  lengths  to  produce  a  virtually  continuous  fabric. 
This,  however,  was  a  manual  operation  performed  upon  the 
finished  paper,  and  the  product  is  only  crudely  suggestive 
of  the  pulp  yarns  which  have  been  evolved  through  various 


WOOD   PULP  AND   THE  TEXTILE  INDUSTRIES     221 

stages  of  perfection  by  the  work  of  European  inventors 
bringing  to  bear  upon  the  problem  the  resources  of  modern 
mechanical  appliances. 

The  development  of  this  industry  is  mainly  due  to  the 
enterprise  of  a  succession  of  German  inventors,  and  an 
excellent  account  of  their  labours  is  contained  in  the 
treatise  of  Prof.  E.  Pfuhl,  "  Papier stoffgarne  (Zellstoffgarne, 
Xylolin,  Silvalin,  Miella)  ihre  Herstellung,  Eigenschaften 
und  Verwendbarkeit,"  published  by  G.  Hoffler,  Eiga, 
1904.  This  treatise  on  "  Paper-pulp-yarns,  their  pre- 
paration, properties  and  applications,"  is  a  very  complete 
technological  account  of  the  matter,  to  which  the  specialist 
student  must  refer.  In  the  general  account  which  follows 
we  have  made  free  use  of  the  matter  of  the  treatise,  and 
we  acknowledge  our  indebtedness  to  the  author  and 
publisher. 

It  appears  that  the  evolution  of  the  industry  is  set  forth 
in  the  subjoined  outline  of  inventions,  as  embodied  in 
German  patents.  Practical  success  is  claimed  to  have  been 
achieved  by  three  of  these  systems,  each  of  which  represents 
a  consolidation  of  two  or  more  patented  inventions  :— 

(a)  The  system  of  Claviez  &  Co.  is  based  upon  a  finished 
but  unsized  paper  as  raw  material.  This  is  cut  into 
fine  strips,  of  a  few  mm.'s  width,  each  strip  being  separately 
wound  on  a  bobbin,  which  is  then  transferred  to  a  spinning 
or  twisting  frame.  In  the  form  of  twist  it  is  subject  to  a 
rolling  process  to  consolidate  the  thread,  and  this  treat- 
ment is  repeated,  after  moistening  the  thread,  in  a  second 
machine,  the  speed  of  which  is  adjusted  to  produce  a  certain 
drawing  effect. 

The   spindle   designed   by   Claviez  for  the  spinning  or 


222 


WOOD  PULP  AND  ITS  USES 


twisting  of  the  paper  strips  is  represented  by  the  accom- 
panying figure  (Fig.  24),  the  spool  or  reel  carrying   the 
paper  strip  of  2 — 3  mm.  width  is  carried  on  the  hollow 
brass  axis  b,  which  is  held  in  position  on  the  spindle  s  by 
means  of  springs.     The  fliers/  rotate  in  the  same  direction 
in  which  the  paper  strip  was  wound 
?  on  the  spool ;  the  strip  is  thus  twisted 

and  drawn  off  through  rollers  under 
suitable  tension.  The  yarns  pro- 
duced under  this  system  are  known 
as  "  Xylolin,"  and  they  are  stated  to 
have  firmly  established  themselves  in 
the  textile  industry,  competing  chiefly 
with  jute  yarns. 

A  considerable  refinement  in  pro- 
duction has  been  aimed  at  in  the  two 
groups  of  inventions  about  to  be 
described,  for  which  the  starting 
point  is  not  a  finished  paper,  but  the 
web  in  the  unfinished  condition  in 
which  it  is  delivered  from  the  press 
rolls  of  the  paper  machine. 

(b)  The  Kellner-Tiirk  system  is  the 
consolidated  result  of  the  inventive 
work  of  the  late  Carl  Kellner,  of  Hallein — a  well-known 
pioneer  of  the  wood  pulp  industry— and  of  G.  Turk,  of 
Bad  Gastein.  The  main  patents  are  those  of  1891 
(D.  E.  P.  73601)  and  1892  (D.  E.  P.  79272)  and  the 
claims  are  similar,  the  former  indicating  the  formation  of  a 
pulp-sliver  by  taking  moist  paper  strips  as  delivered  from 
a  cylinder  paper  machine,  and  subjecting  them  whilst  still 


FIG.    24.— Spindle  for 
twisting  paper-strips. 

a  carries  the  con- 
tinuous length  of  paper 
of  2—3  mm.  width: 
//  are  the  fliers. 

(Claviez&Co.,D.  E.  P. 
93324.) 


WOOD  PULP  AND  THE  TEXTILE  INDUSTRIES       223 

on  the  cylinder  wire  to  a  rubbing  and  rolling  treatment  by 
which  they  are  rounded  and  consolidated  ;  the  latter  patent 
indicates  the  same  general  plan  of  manufacture,  but  the 
rolling  of  the  strips  takes  place  after  they  have  left  the 
machine  wire.  The  production  of  the  paper  or  pulp  strips 
is  not  patented.  This  is  effected  by  the  special  construction 
of  the  wire  cloth  of  the  paper-making  cylinder,  which  is  an 
alteration  of  impervious  brass  strips  with  the  ordinary 
60  —  70-inch  mesh  wire  cloth  ;  the  pulp  is  deposited 
on  the  latter  only.  These  patents  were  acquired  in  1900 
by  the  Patentspinnerei  A.G.,  in  Altdamm,  Stettin,  in  whose 
hands  the  process  was  further  developed  in  the  direction  of 
the  Tiirk  patent. 

The  main  feature  of  the  treatment  of  the  strips  is  the 
process  of  conversion  from  the  flat  to  the  cylindrical  form, 
under  which  there  is  an  incidental  consolidation  of  the 
fibrous  aggregate.  This  effect  is  produced  by  passing  the 
strips  through  a  special  apparatus,  the  principle  of  which 
may  be  traced  to  an  invention  of  0.  Schimmel  &  Co., 
Chemnitz,  described  in  the  German  patent  76126,  above 
cited.  The  invention  was  in  its  inception  applied  to  the 
"  lap  "  of  dry-carded  short  fibre  as  delivered  from  a  textile 
carding  machine.  The  lap  delivered  at  the  full  breadth  of 
the  card  is  received  between  a  pair  of  rollers  which  divide 
it  by  a  peripheral  cutting  arrangement  into  narrow  strips, 
which  pass  forward  to  the  rolling  apparatus.  This  consists 
of  an  upper  and  under  endless  band  of  leather  in  close 
contact,  disposed  for  motion  in  the  horizontal  plane,  each 
round  a  pair  of  rollers  moving  in  geared  connection.  The 
rotation  of  these  rollers  carries  forward  the  now  divided 
strips,  but  an  alternating  movement  in  the  direction  at 


224 


WOOD   PULP  AND  ITS   USES 


right  angles  is  communicated  to  the  leather  bands  by 
eccentrics,  and  this  movement  is  in  turn  communicated  to 
the  strips  as  they  travel  forward,  under  which  they  are 
continuously  rubbed  and  rolled  into  cylindrical  form.  They 


FIG.  25. — Machine  for  rolling  flat  strips  of  prepared  short  fibre 
(sliver).  The  "  lap  "  is  taken  from  the  card  P,  sub-divided  into 
strips  in  passing  R  R,  rolled  at  N  N,  and  delivered  into  cylin- 
drical boxes  or  cans,  T  T.  (O.  Schimmel,  D.  R.  P.  76126.) 

are  then  suitably  laid  down  in  receivers,  to  be  transported 
to  the  spinning  or  twisting  frames  (see  Fig.  25). 

On  the  Kellner-Tiirk  system,  as  applied  to  the  wet  pulp 
strips,  a  similar  apparatus  and  process  succeeds  the  press- 
rolls  of  the  paper  machine.  The  endless  bands  of  the 
rubbing  and  condensing  rollers  are  in  this  case  made  of 
indiarubber. 


WOOD  PULP  AND  THE  TEXTILE  INDUSTRIES     225 

The  third  operation,  that  of  spinning  or  twisting,  is 
carried  out  on  the  still  moist  thread.  There  are  various 
devices  employed  in  the  textile  industry  for  conferring  the 
high  degree  of  twist  which  characterises  the  textile  yarns 
in  their  final  forms ;  the  same  principles  and  forms  of 
machine  are  pressed  into  the  service  of  the  paper-pulp- 
spinner.  The  twisting  is  mostly  carried  out  on  "  Kingzwirn- 
maschinen,"  ring-spindle  machines,  i.e.,  frames  carrying 
60  —  70  spindles  on  the  side.  In  making  weft  yarns, 
the  delivery  of  the  spun  yarn  is  varied  so  that  it  may 
be  wound  directly  into  cops,  or  on  to  tubes  placed  over 
the  spindles.  There  are  two  limitations  to  the  efficiency 
of  this  system;  one  is  in  the  mode  of  making  the  pulp 
strips  on  a  cylinder  machine.  The  alternative  process  and 
machine,  based  on  the  flat-running  Fourdrinier  wire,  with 
its  much  higher  productive  efficiency,  is  adopted  by  them 
as  the  basis  of  the  competing  system  which  we  shall  next 
describe.  The  contrast  of  these  two  methods  of  converting 
beaten  pulp  into  paper  is  well  set  forth  in  C.  Hof man's 
Handbuch  der  Papierfabrikation,  ed.  1897,  page  858. 

The  second  limitation  of  efficiency — that  is,  in  output  and 
therefore  economic  production — is  in  the  speed  of  the 
machine  and  process  of  rounding  and  consolidating  the 
strips.  Taking  12 — 15  m.  per  minute  as  the  speed  of 
running,  a  machine  of  80  spindles  will  produce  in  length 
from  12  X  80  X  60  X  24  =  1,382,400  m.  to  15  X  80  X 
60  X  24  =  1,728,000  m.  per  diem :  these  lengths  represent 
460  to  576  kilos,  of  a  No.  3  yarn,  or  115  to  144  kg.  of  a 
No.  12  yarn.  In  actual  working,  allowance  has  to  be  made 
for  unavoidable  breaks  and  stoppages,  and  the  output  is 
taken  at  30  per  cent,  less  than  these  figures.  It  may  be  noted 

W.P.  Q 


226  WOOD  PULP  AND  ITS  USES 

that  a  beating  engine  (Hollander)  of  160  to  200  kg. 
capacity  (dry  pulp),  dealing  with  four  charges  in  the  twenty- 
four  hours,  would  feed  two  of  such  special  machines. 

In  summing  up  his  notice  of  this  system,  Prof.  Pfuhl 
expresses  himself  as  follows  (page  33) : — "  It  is  probable 
that  a  number  of  circumstances,  in  addition  to  the  not  very 
satisfactory  output  of  the  sliver  machine,  have  contributed 
to  the  present  position  (end  of  1906)  of  the  system,  which 
is  that  after  many  years  of  existence,  as  indicated  by  the 
dates  of  the  patents,  it  remains  without  industrial  extension." 

In  connection  with  the  development  of  the  Kellner-Tiirk 
process,  a  number  of  patents  have  been  taken  by  Leinweber, 
which  have  been  acquired  by  the  Altdamm  Company.  These 
inventions  have  reference  to  details  which  are  found  to  be 
essential  factors  of  economic  production,  such  as  the  sub- 
division of  the  web  of  pulp  into  small  strips  (D.E.P.  140011). 
The  mode  of  distributing  these  to  the  further  operations 
(140,666)  a  further  patent  (140012)  has  reference  to  the 
rounding  of  the  strips  to  a  sliver  by  causing  them  to  pass 
through  a  funnel>  the  tube  of  which  is  of  spiral  or  other 
special  construction,  this  treatment  immediately  preceding 
the  spinning  or  twisting. 

System  oi'  E.  Kron.     "  Silvalin  "  yarns. 

It  will  have  been  evident  during  this  discussion  that 
wood-pulp  "  spinning  "  is  a  hybrid  process :  a  cross  adapta- 
tion of  well-known  paper  making  and  textile  methods  to 
the  production  of  a  particular  type  of  fabric,  and  involving 
in  a  very  special  sense  the  question  of  cost  of  production. 
It  may  be  noted  in  illustration  of  this  point  that  while 
papers  and  staple  textiles  are  produced  and  sold  under  a 
very  wide  range  of  costs  and  prices,  the  new  industry  in 


WOOD  PULP  AND  THE  TEXTILE  INDUSTEIES     227 

the  hybrid  products  depends  mainly  upon  cost  of  production. 
The  system  which  consolidates  the  inventions  of  Messrs. 
Kron  claims  important  progress  in  this  essential  element  of 
success.  In  the  first  place,  the  production  of  the  original 
pulp-strips  is  "intensified"  by  employing  the  ordinary 
Fourdrinier  machine  at  its  full  width,  the  web  being  sub- 
divided into  narrow  strips  by  an  arrangement  for  projecting 
jets  of  water  upon  the  web  at  such  distances  that  the  web 
is  divided  into  100 — 500  strips  per  metre.  The  separation 
of  the  strips  is,  however,  not  thus  completed ;  they  are 
wound  up  on  a  roll  of  the  full  width,  and  are  afterwards 
separated  and  detached  as  discs.  It  is  based  upon  the 
following  patents,  of  which  the  subject-matter  indicates  the 
essence  of  the  several  inventions  :— 

I.  Main  patent  (K.  23200  vii/76c).    A  process  for  twisting 
or  spinning  the  cellulose  (pulp)  directly  from  pulp-rolls. 

(a)  Addition-patent  I.  (K.  23887  vii/76c)  for  winding  up 

the  wet-web  at  the  breadth  of  the  machine  to  be  after- 
wards divided  in  pulp-discs  of  suitable  narrow  width. 

(b)  Addition-patent  II.   (K.  23926,   vii/76c).     Improve- 

ments in  the  manufacture  of  pulp-rolls  in  a  moist 
but  coherent  state. 

II.  Main    patent    (K.    25168,    vii/76c).      Process    and 
apparatus  for  winding  up  moist  strips  of  paper  pulp,  etc. 

III.  Main  patent  (K.  25043).     Process  and  apparatus  for 
sub-dividing  a  web  of  pulp  (as  on  the  wet  end  of  a  paper 
machine)  into  strips. 

IV.  Main    patent    (K.    26001).      Apparatus  for    direct 
delivery  of  moist  pulp  strips. 

V.  Main  patent  (K.   25036).      Spinning    machine    for 
preparation  of  detachable  cops. 

Q  2 


228  WOOD  PULP  AND  ITS  USES 

The  succession  of  operations  in  the  Kron  system  is  as 
follows : — 

1.  The  formation  of  the  web  on  the  Fourdrinier  wire ; 
its  sub-division  into  strips  by  the  impact  of  jets  of  water 
for  the  number  of  strips  required  to  be  formed. 

2.  The  pulp-strips  are  subjected  to  the  action  of  press- 
rolls   for  the   gradual   removal   of  water  and   progressive 
solidification  of  the  fibrous  aggregate;  it  is  then  further 
dried  by  heat  on  a  steam-heated  cylinder  ;  and  then  wound 
up  in  what  is  termed  a  magazine  roll,  which  thus  holds  a 
series  of  discs  in  close  contact.     These  are  detached  as 
required   for   the   further  operation  of  twisting,  and  are 
disposed  for  winding  off  in  a  horizontal  or  inclined  position 
beneath  the  spindles. 

3.  The  winding  off  and  twisting  involves  the  passage 
through  the  machine  which  is  the  subject-matter  of  patent 
No.  4  (ante)  from  which  the  strips  are  delivered  continuously 
to  the  spindles.      These  have  a  speed  of  3,000  to  8,000 
revolutions  per  minute,  with  the  sliver  travelling  at  8  to  16 
metres  per  minute,  according  to  the  size  of  the  yarn  and 
the  degree  of  twist  required. 

The  following  table  of  results  of  tests  of  tenacity  and 
"  elasticity "  more  particularly  illustrates  the  technical 
features  of  the  wood-pulp  "  spinning  "  systems  :— 

Metrical  count.      Breaking  strain      Extensibility 

in  terms  of  per  cent, 

breaking  length. 

Silvalin  strips  (dry)  .  2,891  2,390  3'06 

,,       yarn.         .  .  2,900  4,810  6 '44 

Altdamm  (Turk)  strips  .  13,153  4,170  2 "84 

Strips  rounded  (sliver)  .  8,222  5,014  2'24 

„  .  8,408  5,187  2-71 

Finished  yarn         .  .  12,100  6,413  3'06 


WOOD  PULP  AND  THE  TEXTILE  INDUSTRIES     229 

From  his  extended  investigations  of  these  products  Prof. 
Pfuhl  concludes  that  this  class  of  yarns  made  from  pure 
wood-cellulose  have  a  mean  breaking  length  of  5  to  7  km. 
with  an  extensibility  of  6  to  7  per  cent. ;  and  these  constants 
define  a  textile  quality  sufficiently  high  for  their  utilisation 
under  the  ordinary  conditions  of  wearing,  both  as  warp  and 
weft.  The  warps  of  wood-pulp  yarns  require  no  previous 
"  dressing "  or  sizing.  The  finished  fabrics,  it  may  be 
mentioned,  have  about  one-half  the  strength  of  jute  fabrics 
of  the  same  make  and  weight.  In  regard  to  the  conditions 
of  utilisation  of  such  fabrics,  it  is  to  be  noted  that,  when 
wetted,  they  lose  their  tensile  quality  entirely ;  and  although 
they  regain  their  strength  in  drying,  it  is  evident  that  the 
defect  in  question  is  a  serious  limitation  of  their  utility. 

(b)  Cost  of  Production  of  Silvalin  Yarns. — The  estimates 
of  Prof.  Pfuhl  are  based  upon  a  daily  output  of  6,000  kg. 
or  1,800  tons  per  annum,  involving  2,160  spindles  running 
eleven  hours  ;  the  corresponding  production  of  sliver-strips 
running  continuously,  i.e.,  twenty  to  twenty-four  hours  per 
day.  In  the  estimates,  the  production  of  a  No.  3  (metrical) 
yarn  is  considered.  The  capital  outlay  is  summarised  as 

follows : — 

Marks. 

Site  and  land,  15,000  kr 15,300 

Buildings,  2,000  mr.,  etc.            71,400 

Machinery  and  plant       309,500 

Business  capital    ...         ...         ...         ...  126,800 

523,000 

These  represent  an  annual  charge  of  about  36,000  m.  and 
adding  salaries  the  establishment  represents  a  charge  of 


230  WOOD  PULP  AND  ITS  USES 

56,807  m.  per  annum.  Wages  are  estimated  at  60,320  m., 
and  coal  (at  20  m.)  43,160,  adding  for  lighting,  packing,  etc., 
41,000  m.  The  total  annual  charge  is  201,287  m.  This 
on  the  basis  above  set  forth  gives  a  cost  of  production  per 
ton  of  111*83  marks.  Adding  20  marks  for  one  patent 
licence,  we  have  a  total  cost  of  131'83  marks.  Comparing 
these  costs  with  those  of  spinning  jute  to  yarn  of  the  same 
count,  which  was  estimated  at  100  to  120  m.  under  similar 
conditions,  it  is  seen  that  they  are  some  10  to  20  per  cent. 
higher.  The  respective  raw  materials  have  now  to  be 
brought  into  account,  viz.,  sulphite  cellulose  at  15  to  18  m. 
per  100  kg.,  and  jute  at  £10  to  £14  per  ton.  The  final 
comparison  is  made  in  the  following  terms  :—  - 

Marks  for  100  kilos. 

.  /Jute  warp  yarn,  No.  6...  34  43 
Total  cost  of     ,   . 

.     A.        i  Jute  weft  yarn,  No.  5,  4  31  39 

production     \silvalin  yarn>  No.5(  5...  28  82 

Physical  Properties  and  Application  of  Wood-pulp  Yarns 
and  Fabrics.  —  It  has  already  been  indicated,  and  is,  in  fact, 
more  or  less  self-evident  that  wood-pulp  yarns  are  limited 
in  their  utility.  In  measuring  the  utility  a  number  of 
general  principles  have  to  be  taken  into  account  as  well  as 
the  practices  and  conventions  of  the  textile  industry  which 
follow  from  them.  The  numerical  basis  of  measurement  or 


the  "counts  of  yarn"  is  the  ,    relationship,  which 

in  the  textile  industry  takes  a  number  of  conventional  forms. 
The  trade  in  coarse  yarns  which  alone  come  into  considera- 
tion here,  is  mainly  concerned  with  flax,  hemp  and  jute  or 
bast  fibre  yarns,  and  low  grades  of  cottons.  Thus  we  have 


WOOD  PULP  AND  THE  TEXTILE  INDUSTKIES      231 

the  English  units  or  yarn  numbers  for  bast  fibre  yarns  = 
the  number  of  leas  (of  300  yards)  in  the  pound ;  for  cottons 
the  number  of  hanks  (of  840  yards)  in  the  pound.  The 
jute  trade  (Dundee)  takes  an  inverse  measure  in  terms  of 
the  "  spindle  "  of  14,400  yards,  the  number  of  pounds  in 
this  length  being  the  yarn  number.  For  wood-pulp  yarns 
the  simpler  metrical  numeration  obtains,  viz.,  the  number 
of  metres  (unit  of  length)  to  the  gram  (unit  of  weight). 
The  following  table,  of  the  metrical  yarn  numbers  and 
their  equivalent  in  the  conventional  units  will  be  found 
useful. 

Table     of    equivalent    yarn     "numbers"    or    yei£ht 

length 

description  compared  with  metrical  counts. 

Metrical  counts  :       Cotton  count :        Flax  counts  :        Jute  counts  : 


metres  per 
Igrm. 

n.  (840)  yds. 
per  Ib. 

n.  (300)  yds. 
per  Ib. 

Ibs.  per 
14,400  yds. 

1-0 

0-691       ... 

1-654 

...       29-0 

1-693     ... 

1-0 

2-800 

...       17-1 

0'605     ... 

0-357       ... 

1-0 

...       48-0 

29-0 

17-1 

48-0 

I'O 

The  strength  or  "  tenacity  "  of  yarns  is  determined  as  a 
breaking-strain,  but  usually  expressed  as  a  breaking-length, 
that  is,  the  length  of  the  breaking-weight  of  the  yarn  itself. 
This  is  comparable  at  once  with  the  sectional  breaking- 
strain  usually  applied  to  solid  substances.  For  where  L 
expresses  breaking-length,  s  specific  gravity,  and  k  the 
breaking-strain  per  1  mm.  of  sectional  area,  L  X  s  =  k. 

Breaking-Length. — It  is  an  expression  which  eliminates 
two  of  the  three  dimensions,  that  is,  it  is  independent  of 
the  sizes  of  yarns  or  threads,  as  of  the  thickness  or  width 


232  WOOD  PULP  AND   ITS  USES 

of  fabrics  such  as  paper  produced  in  sheet  or  web.  It  will 
be  noted  as  a  conventional  expression,  but  of  very  great 
"  convenience,"  and  gives  a  comprehensive  or  aggregate 
expression  of  tensile  quality,  and  thus  is  applicable  to  the 
most  diverse  substances  and  in  their  most  varied  form. 

Fracture  of  a  textile  yarn  or  paper  is  accompanied 
always  by  elongation  under  the  strain ;  this  of  course  is  a 
certain  measure  of  true  elasticity.  The  latter  would  be 
denned  as  the  amount  of  extension  of  which  the  fabric  is 
capable,  with  the  condition  of  reverting  to  its  former  dimen- 
sions when  the  strain  is  removed.  This  quality,  however, 
is  seldom  denned  or  tested  in  textile  fabrics. 

Extensibility  is  usually  expressed  as  the  total  percentage 
elongation  sustained  at  or  under  the  breaking-strain. 

The  following  table  of  these  quantities  applies  to  the  most 
important  textiles. 

Breaking  Length. 

Kilometres.        Elasticity. 

Cotton  yarns          . .          . .   13—14  3'97 

Eamie  yarns  . .          . .    11—12  0'8— 1-8 

Flax  yarns,  wet  spinning ..    12'4 — 19'5     I'l — 1'8 


Mean  averages  for 

Commercial 

Products. 


Flax   and  tow  yarns,   dry 

spinning ll'S— 12*4  2'5— 3'7 

Jute  yarns 9'9  2'0 

Lustra  cellulose  average  . .         12*0  2'0 

Artificial  silks,  extremes..  8'0— 14'0  7'0— IS'O 


The  mechanical  properties  of  papers  are  expressed  in  the 
same  terms,  and  it  is  interesting  to  compare  the  range  of 
numbers  for  the  highest  classes  of  papers : — 

Breaking  Length.  Elongation. 
Metres.  Per  cent. 

Bag  papers,  Manila  papers   and 

wood  pulp  papers  (air  dry)     ...4,000—8,000    ...     3'8 
It  is  evident  from  these  numbers  that  the  shorter  units 


WOOD   PULP  AND  THE  TEXTILE  INDUSTRIES     233 

common   to  papers   produce   a  texture  approximating  in 
mechanical  properties  to  the  lower  grades  of  spun  yarn. 

From  the  preceding  expose  it  would  appear  that  inventors 
have  endeavoured  to  overcome  the  unfitness  of  paper  as 
such  for  textiles,  or  weaving  uses,  by  changing  the  form  and 
usual  dimensions  of  the  web  of  paper.  The  stages  in  the 
productions  of  a  cylindrical  product  or  yarn  are  (1)  cutting, 
(2)  rolling  and  (3)  subjecting  the  cylindrical  rolled  strips  to 
a  twisting  process  whilst  in  a  moist  condition.  The  effects 
of  these  treatments  in  increasing  the  solidity  and  resistance 
of  the  agglomerates  is  shown  by  the  following  figures : — 

Breaking  Length.  Elongation. 
km.1  Per  cent. 

Plane  strips,  dried  4'17      ...      2'84 

Rolled  into  cylindrical  form       ...         5*18      ...      2*71 
Rolled  and  twisted          6'41      ...      3'06 

The  following  numbers  have  reference  to  wood-pulp  yarns 
as  industrially  prepared : 
Silvalin  (Kron  process,  1903 — 4) : 

Mean  of  240  tests         5'498     ...       6'8 

Maximum  observed       ...         ...         8'314     ...     10*5 

Minimum  observed        4*10       ...       2*9 

Altdamm  (Turk  process,  1903—4) : 

Mean  of  90  tests  6'159     ...       7'71 

Maximum  observed       7*695     ...     1T16 

Minimum  observed        3'619     ...       4*38 

As  a  chemical  individual  wood  cellulose  differs  but  little 

from  cotton  cellulose  ;  and  when  only  chemical  relationships 

are  involved,  there  is  an  obvious  probability  of  the  former 

being  able  to  substitute  cotton  as  a  basis  of  manufacture. 

1  Km.  is  the  contraction  for  kilometre. 


234  WOOD  PULP  AND   ITS  USES 

For  such  substitution  there  is  always  the  inducement  of 
relatively  low  market  price. 

SPECIAL  CELLULOSE  INDUSTRIES. 

There  are  several  important  industries  which  have  been 
developed  upon  the  characteristic  properties  of  derivatives 
of  cotton  cellulose.  The  modern  industry  of  high  explosives 
is  based  upon  the  nitric  esters  of  cotton,  which  in  certain 
cases  are  associated  with  the  corresponding  nitrates  of 
glycerine.  As  shown  in  Chapter  II.  cotton  can  be  nitrated, 
that  is,  combined  with  nitric  acid  by  simple  methods  and 
without  any  evident  structural  change.  The  nitro-cotton, 
or  gun  cotton,  has  the  external  appearance  of  ordinary 
cotton,  but  is  harsher  to  the  touch,  and  the  addition  of  the 
large  weight  of  70  or  80  per  cent,  due  to  the  combination 
with  nitrate  groups,  causes  minor  structural  changes  which 
can  be  well  observed  under  the  microscope. 

The  properties  of  gun  cotton  are  primarily  those 
associated  with  rapid  or  explosive  combustion ;  combination 
with  the  nitric  groups  introduces  so  much  oxygen  into  the 
molecule  that  the  new  compound  has  all  the  elements  or 
internal  conditions  for  complete  combustion,  whereas 
ordinary  combustion  depends  upon  the  gradual  supply  from 
without  of  atmospheric  oxygen  to  the  burning  body.  When 
gun  cotton  is  fired,  there  is  a  rapid  propagation  of  the 
combustion,  and  when  this  takes  place  in  an  enclosed 
space  detonation  occurs,  with  rupture  of  any  containing 
vessel,  due  to  the  enormous  development  of  gas1  at  high 
temperature. 

1  The  products  of  explosion  of  the  nitrate  are  represented  by  the 
equation  2  C24H18O9  (NO8H)U  =  24  CO  +  24  COa  +  17  H2  +  12  H20 
+  11  Na  and  the  heat  evolved  is  2,200  calories  per  1  gramme. 


WOOD   PULP  AND  THE  TEXTILE    INDUSTRIES     235 

The  cotton  nitrates  are  soluble  in  a  number  of  organic 
liquids  in  which  they  swell  up  and  pass  into  homogeneous 
solution ;  with  limited  proportion  of  such  solvents,  and 
mechanical  means,  the  fibrous  nitrates  may  be  worked  up 
into  structureless  plastic  masses,  which  can  be  drawn  or 
moulded  into  threads  or  rods,  or  rolled  into  sheet.  It  is  an 
important  discovery  that  glycerine  or  nitro-glycerine  is  a 
solvent  of  mtro-cellulose.  Nitro-glycerine  resembles  nitro- 
cotton  in  fundamental  combustibility,  and  is  similarly  a 
high  or  blasting  explosive,  even  more  powerful  than  nitro- 
cotton,  owing  to  the  somewhat  higher  relative  proportion 
of  oxygen.  It  sounds  like  a  paradox  that  on  bringing  these 
two  high  explosives  together  a  mixture  results  which  has  the 
properties  of  restrained  combustion,  or  regulated  explosion. 
These  bodies  worked  together  in  suitable  proportions  pro- 
duce a  plastic  mass  which  can  be  drawn,  as  above  stated,  or 
shaped.  When  flame  is  communicated,  there  is  a  regulated 
combustion  proceeding  from  the  external  layers  to  the 
centre  of  the  mass.  Explosives  of  this  order  can,  in 
fact,  be  used  as  propulsive  explosives,  that  is  for  military 
ammunition ;  the  ordinary  forms  are  cordite,  balistite,  etc. 

It  would  appear  to  be  possible  to  replace  cotton  for  the 
manufacture  of  nitro-cotton  by  the  wood  celluloses,  but 
there  are  many  reasons,  partly  of  constitution,  and  partly 
having  to  do  with  the  external  characteristics  or  fibrous 
forms,  which  have  prevented  this  from  taking  any  deep 
root,  and  we  can  therefore  hardly  enter  into  the  specialised 
technology  of  gun  cotton  and  explosives  as  a  development 
of  wood-pulp  industry. 

The  same  may  also  be  said  of  the  very  important 
industry  in  articles  known  as  celluloid,  xylonite,  etc.  This 


236  WOOD  PULP  AND  ITS  USES 

art  and  industry  is  based  upon  the  plastic  qualities  of 
nitro  cellulose  when  treated  with  suitable  solvents,  and 
the  plastic  mass  obtained  by  incorporating  the  fibrous 
nitrates  with  special  solvents  and  completing  the  mixture 
to  a  homogeneous  mass  by  means  of  mechanical  appliances, 
can  be  shaped  into  any  required  form.  There  are  particular 
reasons  why  this  industry  also  has  not  availed  itself  of  the 
supplies  of  wood  cellulose  of  which  the  market  value  is 
approximately  one- third  that  of  the  forms  of  cotton  which 
are  ordinarily  used. 

These  reasons,  as  previously  indicated,  are  partly  in  the 
relative  inconvenience  of  handling  the  short  fibres  of  the 
wood  celluloses  :  and  partly  from  the  particular  features  of 
instability  characterising  compounds  which  are  potentially 
self-destructive.  Gun  cottons  and  the  lower  nitrates  of 
cotton  are  "  unstable "  as  originally  produced  owing  to 
the  presence  of  sulphuric  acid  residues  in  combination. 
These  are  eliminated  by  exhaustive  washings  and  successive 
boilings  with  water.  When  so  purified  and  "  sterilised  " 
they  may  be  kept  for  prolonged  periods  without  change. 

But  other  celluloses  are  constitutionally  differentiated 
from  the  normal  cotton  cellulose,  and  contain  a  proportion 
of  groups  of  less  intrinsic  stability :  these  nitrated  to 
the  same  degree  are  correspondingly  less  stable,  and  liable 
to  spontaneous  decomposition.  Hence  a  lower  stability 
of  the  entire  complex  and  unsuitability  for  these  industrial 
uses. 

Cellulose  Acetates. — The  highly  combustible  and  explosive 
nature  of  the  cellulose  nitrates  imports  a  considerable 
danger  in  the  manufacture  and  use  of  celluloid  or  xylonite. 
An  important  use  of  the  nitrates  is  for  the  manufacture  of 


WOOD   PULP  AND   THE   TEXTILE   INDUSTEIES      237 

photographic  films,  and  in  ordinary  use  this  has  not  led  to 
any  serious  catastrophe.  On  the  other  hand,  the  film 
employed  to  carry  the  photographic  picture  in  the  kine- 
matograph,  the  picture  being  projected  on  to  a  screen  by 
means  of  powerful  illuminants,  is  a  combination  of  risks, 
which  has  led  to  several  disasters.  It  is  a  well-known 
objective  of  inventors  to  discover  an  efficient  substitute 
for  the  nitrate.  Cellulose  acetate  is  an  ester  of  cellulose 
which  is  a  close  analogue  of  the  nitrate,  is  also  soluble  in 
organic  solvents,  and  may  be  shaped  in  admixture  with 
these  in  any  desired  way.  The  first  serious  attempts  to 
prepare  the  cellulose  acetate  on  the  industrial  scale  date 
from  1890.  It  was  found  by  ourselves  that  certain  forms 
of  cellulose  can  be  brought  into  reaction  with  acetylating 
reagents  in  presence  of  zinc  acetate,  and  such  process  was 
carried  out  on  an  industrial  scale. 

Further  investigations  of  other  chemists  led  to  the 
observation  that  cellulose  combines  readily  with  acetic 
anhydride  in  presence  of  sulphuric  acid  relatively  in 
small  quantity,  and  taking  part  only  in  determining  the 
main  reaction.  Such  a  process,  the  subject  of  a  series  of 
patents  by  Lederer  (see  p.  240),  has  led  to  considerable 
economy  in  the  production  of  the  acetate,  and  the  matter  is 
being  industrially  developed  in  one  or  two  countries.  The 
acetate  film  answering  all  the  requirements  of  photographic 
use  is  still,  however,  in  the  embryo  stage  of  development. 

Owing  to  the  simplicity  of  the  reaction  and  the  relative 
inertness  of  acetyl  groups,  there  is  every  reason  why  the 
wood  celluloses  should  answer  all  requirements  for  this 
industry.  The  reaction  is  usually  carried  out  with  a 
mixture  of  glacial  acetic  acid  and  acetic  anhydride  in  equal 


238  WOOD  PULP  AND  ITS  USES 

proportions  to  which  the  calculated  small  quantity  of 
sulphuric  acid  is  added  (Lederer) ;  in  contact  with  this 
reactive  mixture,  the  celluloses  are  gradually  and  pro- 
gressively attacked  and  pass  into  solution  :  Low  tempera- 
tures only  are  required,  and  50°  C.  is  the  general  maximum. 
The  product  is  obtained  as  a  highly  viscous  liquid,  that  is,  a 
solution  of  the  ester  in  the  excess  of  the  reactive  mixture. 
The  mixture  is  treated  with  water,  which  precipitates  the 
ester,  and,  by  suitable  mechanical  means,  this  is  effected  in 
a  state  of  minute  subdivision  of  the  ester,  so  that  it  is  easily 
washed.  When  dry  it  dissolves  to  bright  solutions  in  its 
special  solvents,  which  are  chloroform,  ethylene  chlorides, 
acetic  acid,  phenol,  etc.  It  is  to  be  noted  that  these 
solvents  present  difficulties  in  use,  and  they  are  by  no 
means  so  convenient  as  the  solvents  used  for  the  nitrates. 
Variations  of  the  process,  however,  have  led  to  the  pro- 
duction of  acetates  soluble  in  acetone,  a  solvent  which  is 
free  from  objection  in  use. 

An  important  question  of  cost  necessarily  enters  as 
determining  the  extent  of  application  of  these  bodies. 
Owing  to  the  relative  high  price  of  acetic  anhydride,  and 
the  necessity  of  using  an  excess  of  reaction  mixture,  the 
costs  of  acetate  obtained  as  above  described  is  relatively 
high.  In  employing  solvents,  which  are  lost  in  the  working 
of  the  acetate  to  particular  forms,  the  cost  is  added  to. 

Whereas  cellulose  nitrates  can  be  bought  in  the  open 
market  at  from  Is.  to  2s.  per  lb.,  the  acetates  stand  at  a 
multiple  of  these  figures,  viz.,  6s.  to  9s.  a  lb. 

It  is  evident  that  such  prices  exclude  applications  save 
such  as  are  relatively  independent  of  cost. 

Another   point   to   be   noted   in  connection   with   these 


WOOD   PULP  AND  THE   TEXTILE  INDUSTRIES      239 

acetates  is  that  while  the  reaction  is  direct,  and,  in  one 
sense,  simple,  there  is  no  doubt  that  the  use  of  acid 
catalysts  brings  about  the  breaking  down  of  the  cellulose 
aggregate  by  hydrolytic  change,  from  which  results  a  loss 
of  structural  properties.  The  acetates  so  produced  and 
converted  into  continuous  solids  are  relatively  brittle. 

Processes  which  overcome  these  objections  depend  upon 
the  use  of  neutral  or  saline  catalysts,  such  as  zinc  chloride. 
These  appear  to  determine  the  ester  reaction  under  con- 
ditions which  do  not  involve  hydrolysis  or,  at  least,  involve 
it  to  a  much  less  extent.  The  products  of  such  reactions 
are  what  may  be  considered  the  normal  series  of  acetates. 
The  reaction  of  cellulose  with  acetic  anhydride  in  the 
presence  of  zinc  chloride  as  catalyst,  and  glacial  acetic  acid 
as  diluent  can  be  observed  through  a  remarkable  series  of 
gradations  up  to  the  extreme  or  maximum  point.  If  cotton 
is  used,  or  more  particularly  cotton  yarn,  it  is  easily  seen 
that  the  lower  acetates  are  formed  without  any  sensible 
modification  of  the  cellulose  or  yarn.  Acetyl  groups  may 
be  introduced  into  the  cellulose  molecule  with  an  increase  of 
weight  up  to  26  to  36  per  cent.,  producing  an  acetylated 
derivative  unchanged  as  to  form,  showing  certain  new 
properties  in  respect  of  lower  attraction  for  atmospheric 
moisture,  and  for  those  colouring  matters  which  dye  cotton 
directly.  When  carried  to  higher  stages,  the  further  intro- 
duction of  acetyl  groups  cause  a  notable  swelling  of  the 
cellulose,  and,  finally,  as  the  stage  of  tri-acetate  is  reached, 
the  product  passes  into  solution.  This  method  of  acetyla- 
tion  is  economical  by  reason  of  the  fact  that  there  is  a  very 
high  utilisation  of  the  acetic  anhydride. 

A  further  point  of  economy  arises  in  the  application  of 


240 


WOOD  PULP  AND  ITS  USES 


the  acetate,  since  for  certain  purposes  the  reaction  mixture 
itself  can  be  employed.  This  avoids  the  process  of  separa- 
tion of  the  ester,  in  which  the  solvent  is  lost,  or  so  diluted 
as  to  have  a  much  depreciated  value  ;  and,  moreover,  the 
separated  ester  requires  again  to  be  treated  with  solvents, 
which  become  an  added  cost.  These  difficulties,  which 
appear  of  small  magnitude,  have  effectually  impeded  the 
development  of  the  applications  of  the  product.  A  general 
bibliography  on  the  subject  since  1895  will  indicate  the 
directions  in  which  specialists  may  inquire  for  evidence  of 
the  influence  of  these  difficulties  on  the  evolution  of  this 
cellulose  ester. 


GENERAL  BIBLIOGRAPHY  OF  CELLULOSE  ACETATES. 


Original  papers. 

Schutzenberger  and  Waudin. 

Franchimont. 

Cross  and  Bevan. 

1905  Cross,  Bevan  and  Briggs. 
Haeussermann. 

1906  Ost. 

1907  Berl.  and  Watson  Smith. 

1908  „ 

F.  Beltzer. 
Knoevenagel. 
1895-1905  Cross  and  Bevan. 


The  following  patents. 
1894  Cross  and  Bevan. 
1900  Lederer. 
1902  Landsberg. 
„     Lederer. 
Boesh. 


Comptes  Rendus,  68,  814. 
Berl.  Ber.  12,  2059. 
Journ.  Chem.  Soc.  (1890),  57,  1. 
Berl.  Ber.,  38,  1859,  3531. 
Chem.  Ztg.,  29,  667. 
Zeitsch.  Angew.  Chem.,  19,  993. 
Berl.  Ber.,  40,  903. 
Journ.  Soc.  Chem.  Ind.,  534. 
Her.  Set.,  22,  648. 
Chem.  Zeit.,  32,  810. 
' '  Cellulose. "  '  *  Eesearches  on 

Cellulose,"  I.,        "  Eesearches  on 
Cellulose,"  II. 


E.  P.  96761. 
E.  P.  11749. 
E.  P.  4886. 
E.  P.  7088. 
U.  S.  P.  708457. 


WOOD  PULP  AND  THE  TEXTILE  INDUSTRIES      241 


1903  Miles. 

„     Farbenf.  Elberfeld. 

»  » 

,,     Balston  and  Briggs. 

„     F.  Bayer  &  Co. 

1904  Lederer. 

„     Badische,  A.  S.  F. 

1905  Miles. 

„     Fabr.  Prod.  Chim.  Flora. 

1906  Akt.  Ges.  f.  Anilin. 
„     Farbenf.  Elberfeld. 
„     Corti. 

,,     Lederer. 

»         >» 

„     F.  Bayer  &  Co. 

„     Knoll. 

„      Badische,  A.  S.  F. 

1907  Lederer. 

>»    » 
,,  Fischer. 
Knoll. 


,,     Benne. 

,,      Soc.  Anon.  Explosifs. 

1908  Lederer. 

1909  Knoll. 

„      Donnersmarck,  K.  A.  W. 
,,     Lederer. 


U.  S.  P.  733729. 
U.  S.  P.  734123. 
U.  S.  P.  738533. 
E.  P.  10243. 

E.  P.  7346. 

U.  S.  P.  774677. 

F.  P.  347906. 
E.  P.  19330. 
E.  P.  9998. 

E.  P.  1939;  F.  P.  362721,  368738. 
U.  S.  P.  809935. 
U.  S.  P.  816229. 

E.  P.  19107,  26502. 

F.  P.  368766,  371357. 
F.  P.  371447. 

F.  P.  369123. 

U.  S.  P.  373994,  812098. 

E.  P.  3103. 

F.  P.  374370. 

D.  R.  P.  201907.  . 

E.  P.  2026,  2026A,  2026B. 

F.  P.  373994. 
F.  P.  383636. 

D.  R.  P.  210519. 
F.  P.  385179. 
U.  S.  P.  902093. 
U.  S.  P.  891218. 

E.  P.  7743. 

U.  S.  P.  922340. 

F.  P.  400652. 
E.  P.  11625. 


The  derivatives  above  described  are  themselves  esters  or 
compounds  of  cellulose  and  acid  groups,  and  are  treated  or 
manipulated  as  such.  Thus,  the  solutions  of  both  the 
nitrate  and  acetate  can  be  drawn  or  spun  to  a  thread, 
which,  when  sufficiently  fine,  is  an  artificial  silk.  The 
nitrate  is  the  basis  of  the  earliest,  and  still  very  successful, 

W.P.  R 


242  WOOD  PULP  AND  ITS  USES 

method  of  producing  these  artificial  textiles,  nitro-cellulose 
is  only  a  stage  in  a  cycle  of  industrial  operations.  The 
nitrate  is  readily  denitrated,  that  is,  its  nitro  groups  may  be 
removed  with  regeneration  of  cellulose.  The  earlier  forms 
of  artificial  silks  were  not  so  treated,  or,  at  least,  only 
partially  denitrated,  and  therefore  were  necessarily  highly 
combustible,  if  not  explosive.  This  property  very  con- 
siderably prejudiced  the  earlier  attempts  at  utilising  them  : 
this  form  has,  however,  given  way  to  the  denitrated  or 
cellulose  product,  which  is  now  an  ordinary  staple  textile. 
The  acetate  in  the  form  of  thread  or  artificial  silk  could  be 
used  as  such,  as  it  is  not  more  combustible  than  ordinary 
cotton.  It  is  a  product,  however,  that  is  still  only  an 
industrial  curiosity,  and  has  not  taken  any  prominent 
position,  probably  owing  to  the  cost  of  production  of  the 
original  acetate  which,  for  the  reasons  given,  is  necessarily 
high.  A  further  difficulty  in  the  same  direction  is  the 
added  cost  of  redissolving  the  products  in  solvents,  which 
are  lost  during  the  spinning  process.  There  appears  to  be, 
however,  a  prospect  of  producing  a  thread  to  compete  with 
the  artificial  silks  already  established,  by  spinning  or  draw- 
ing the  original  reaction  mixture  in  the  case  of  the  normal 
series  of  acetates. 

We  have  already  described  a  peculiar  compound  of  cellu- 
lose, which  resembles  the  above  in  being  formed  by  com- 
bination of  cellulose  with  acid  groups ;  but  the  compound 
is  soluble  only  in  alkaline  liquids,  and,  moreover,  is 
unstable,  that  is,  decomposes  spontaneously  with  reforma- 
tion of  cellulose.  This  compound  is  the  sulpho-carbonate, 
or  xanthogenic  ester  of  cellulose,  generally  known  as 
"Viscose."  This  compound  was  described  briefly  in  an 


WOOD  PULP  AND  THE  TEXTILE  INDUSTRIES     243 

early  chapter,  and  its  capabilities  of  regeneration  in  struc- 
tural modifications  were  indicated.  Viscose  has  been  used 
in  a  number  of  industrial  applications,  all  of  which  depend 
upon  this  essential  property.  (1)  In  thread  or  yarn,  it  is 
an  artificial  silk.  (2)  In  plane  or  sheet  form  it  is  a 
transparent  film.  (3)  Solidified  in  masses  it  is  a  solid, 
which,  when  dried,  can  be  shaped  or  turned  in  the  lathe  to 
any  required  form.  The  cellulose  can  also  be  mixed  with 
solid  bodies  in  preparing  mixed  agglomerates  in  which  the 
structural  qualities  of  the  cellulose  as  the  binding  or 
agglomerating  medium  assert  themselves,  even  when 
diluted  with  large  proportions  of  foreign  inert  matters. 
(4)  In  less  definite  forms,  but  exerting  the  same  technical 
effects,  viscose  is  used  in  sizing  paper  and  textiles,  and  for 
various  other  applications. 

For  the  general  reasons  above  stated  these  industries  are 
not  necessarily  connected  with  wood  pulps,  since  they  are 
more  generally  applications  of  cellulose.  As  a  matter  of 
fact,  however,  the  wood  pulps  are  a  most  convenient  form 
of  cellulose  for  the  manufacture  of  viscose,  and  we  may 
therefore  give  a  few  particulars  in  elucidation  of  these 
newer  developments. 

The  first  stage  in  the  "viscose  process"  is  the  conversion 
of  the  cellulose  into  alkali  cellulose  by  treatment  with 
caustic  soda  solution  at  mercerising  strength  (15 '0 — 20'0 
per  cent.  NaOH). 

The  limits  of  composition  of  this  product  are 

Per  cent. 

Cellulose    .        .        .        .        .        25—30 
Caustic  soda  (NaOH)         .        .  \      12-5—15 
Water        .         .        :;   .     .         .         62'5— 55 

B  2 


244  WOOD   PULP  AND  ITS  USES 

There  are  two  methods  of  treating  the  wood  pulp  (cellu- 
lose) with  the  alkaline  lye.  The  first  is  to  reduce  the  wood 
pulp  in  a  kollergang  with  sufficient  water  to  bring  about  the 
disintegration  of  the  sheets,  and  then  add  the  calculated 
quantity  of  caustic  soda  dissolved  in  such  a  quantity  of 
water  as  to  produce  a  mixture  of  the  above  composition. 

The  second  method  is  to  steep  the  sheets  in  excess  of  a 
lye  of  17*5  per  cent.  NaOH,  lift,  drain  from  the  excess, 
press  to  a  calculated  weight,  and  then  grind  in  a  kollergang 
or  mixer  to  secure  even  incorporation  of  the  mercerising 
reagent  with  the  cellulose. 

The  alkali-cellulose  is  a  voluminous  semi-dry  mass 
resembling  bread-crumbs  in  appearance.  It  can  be  stored 
in  masses  without  change  of  composition  by  drainage. 

The  alkali-cellulose  is  protected  during  storage  from 
access  of  atmospheric  air — that  is  from  the  action  of 
atmospheric  carbonic  acid. 

The  second  stage  in  the  process  is  the  reaction  of  the 
alkali-cellulose  with  carbon  bisulphide.  This  takes  place 
spontaneously  at  ordinary  temperature.  It  is  important  to 
carry  out  the  reaction  in  a  closed  vessel  to  prevent  loss  of 
the  very  volatile  bisulphide.  The  vessel  ordinarily  used  is 
of  the  form  and  construction  of  a  churn.  In  dealing  with 
large  masses  it  is  found  of  advantage  to  replace  the  simple 
barrel  or  cylinder  by  a  vessel  of  hexagonal  or  octagonal 
form.  The  charge  of  alkali-cellulose  having  been  intro- 
duced, the  quantity  of  bisulphide  is  poured  upon  the  mass, 
the  vessel  closed  at  the  man-hole  and  slowly  rotated,  to 
secure  even  admixture  and  distribution  of  the  contents. 

The  reaction  is  attended  with  a  rise  of  temperature  of  3 
to  7°  C.  according  to  the  mass,  initial  temperature  and  other 


WOOD   PULP  AND  THE  TEXTILE  INDUSTEIES      245 

conditions  of  reaction.  The  mass  changes  in  colour  to 
yellow,  and  the  action  is  arrested  at  the  moment  that  it 
begins  to  lose  its  voluminous  free  condition. 

The  completed  product  tends  to  agglomerate,  and  for  the 
purpose  of  making  a  solution  it  is  important  that  this  should 
be  stirred  into  water  before  the  stage  of  agglomeration  is 
reached. 

There  are  in  fact  two  ways  of  working  up  the  xanthate : 
the  first  is  by  the  action  of  water  to  a  solution  of  10  to  12 
per  cent,  cellulose  strength,  the  second,  the  agglomeration 
is  completed  by  the  action  of  heavy  masticating  rollers, 
such  as  are  used  in  the  manipulation  of  indiarubber. 

The  latter  method  is,  however,  only  used  in  connection 
with  the  making  of  solids  which  are  shaped  into  cylindrical 
form  as  a  stage  in  the  preparation  of  the  solids  known  as 
viscoid  or  viscolith. 

The  viscose  solution  is  the  starting  point  for  the  prepara- 
tion of  artificial  silk.  For  this  industry  the  crude  solution 
is  subjected  to  filtration  which  requires  to  be  of  a  very 
searching  kind.  In  spinning  or  drawing  the  silk  the 
solution  has  to  pass  through  orifices  of  fine  dimensions,  O'l 
to  0'15  of  a  millimetre,  and  hence  it  is  important  to 
eliminate  all  residues  of  insoluble  matter. 

The  xanthate  or  soda  salt  of  cellulose  xanthogenic  acid  is 
the  basis  of  viscose.  It  is  accompanied  by. by-products  of 
the  original  reaction  and  moreover,  as  it  tends  to  spon- 
taneous decomposition  by  interaction  of  the  alkali  with  the 
sulpho-carbonic  residues  in  combination  with  the  cellulose, 
there  is  an  accumulation  of  these  by-products  at  the  expense 
of  the  xanthates,  which  hold  a  steadily  diminishing  pro- 
portion of  the  characteristic  group.  The  spontaneously 


246  WOOD  PULP  AND  ITS  USES 

diminishing  ratio  of  these  groups  to  the  cellulose  is  attended 
by  diminishing  solubility  of  the  cellulose  complex. 

Further,  the  by-products  are  soda  salts  of  the  carbonic  and 
sulpho-carbonic  series,  and  are  precipitants  of  the  cellulose 
compound.  In  both  directions  therefore  there  is  a  tendency 
for  the  viscose  to  revert  to  the  solid  state. 

A  solidified  viscose  is  a  coagulated  xanthate,  and  may  be 
washed  in  water,  and  then  redissolved  in  caustic  soda 
solution. 

The  final  stage  in  the  reversion  is  cellulose  itself,  which 
is  reached  only  after  prolonged  periods  at  ordinary  tempera- 
tures. 

These  phenomena  are  made  use  of  in  several  of  the 
applications  of  viscose,  as  in  the  engine  sizing  of  paper 
and  the  sizing  and  finishing  of  textiles.  The  decomposition 
is  hastened  by  the  interaction  of  the  soda  salts  with  salts 
of  zinc  or  magnesia,  and  these  are  employed  in  the  process 
of  paper  sizing. 

Another  characteristic  decomposition  is  that  determined 
by  salts  of  ammonia.  Viscose  in  contact  with  sulphate  of 
ammonia  in  solution  interacts  quantitatively ;  the  soda  is 
converted  into  sulphate  and  is  replaced  by  ammonia  (base) 
in  both  the  by-products  and  the  xanthate.  These  ammonia 
compounds  are  extremely  unstable,  and  therefore  there  is  a 
very  rapid  decomposition  of  the  xanthate  to  cellulose 
(hydrate).  This  reaction  is  the  basis  of  one  of  the  methods 
of  spinning  or  drawing  to  artificial  silk. 

Another  method  which  also  fulfils  requirements  of  the 
spinning  process,  is  that  of  treatment  with  acids,  which 
bring  about  a  still  more  rapid  decomposition. 

Notwithstanding    the    rapidity   of   action   the   cellulose 


WOOD  PULP  AND  THE  TEXTILE  INDUSTRIES     247 

hydrate  adapts  itself  perfectly,  and  shows  the  same  con- 
tinuity of  substance  and  resistant  quality  as  in  the  case  of 
the  saline  baths. 

In  regard  to  mechanical  methods,  these  are  two,  in 
principle  and  detail.  1.  The  solution  is  projected  from  a 
fine  glass  tube  :  each  individual  thread  is  thus  formed  apart, 
and  a  certain  number  of  these  are  united  into  a  compound 
thread  by  passing  through  a  glass  loop  in  the  coagulating 
or  decomposing  bath. 

The  compound  thread  with  its  14  to  18  elements  is 
manipulated  in  the  untwisted  state,  in  the  first  instance ;  at 
a  later  stage,  as  a  special  operation,  it  receives  the  twist  of 
100  to  200  per  metre. 

An  ingenious  method  of  combining  these  operations  is 
the  centrifugal  spinning  box  of  Stearn  and  Topham. 

This  is  a  box  of  special  construction  rotating  at  a  high 
rate  of  speed  on  a  vertical  axis.  In  this  case  the  compound 
thread  is  directly  produced  in  the  coagulating  bath  by 
projecting  the  viscose  through  a  plane  cap  or  nozzle  of 
platinum  perforated  with  14  to  18  holes.  Each  hole  con- 
tributes a  thread,  and  these  are  drawn  forward  in  the 
coagulating  bath  as  a  compound  thread,  which  ascends  and 
is  taken  vertically  up  and  down  over  a  glass  roller  to  fall 
into  a  funnel  which  communicates  with  the  rotating  box. 
The  centrifugal  motion  has  the  effect  of  drawing  the  thread 
forward,  twisting  it,  and  laying  it  peripherally  in  the  box 
as  a  hollow  or  annular  cocoon. 

The  hydrated  thread  in  this  "cake"  form  is  removed 
from  the  box  at  intervals,  re-wound  into  skeins  and  further 
manipulated  for  purification  of  the  cellulose. 

The  industrial  applications  of  viscose  necessarily  involve 


248  WOOD  PULP  AND   ITS  USES 

a  multiplicity  of  detail  both  chemical  and  mechanical. 
Chemically,  the  product  is  difficult  to  handle  by  reason  of 
its  alkalinity  and  the  large  proportion  of  derivative  sulphur 
containing  groups  which  are  characteristic  of  the  product 
and  by-products. 

When  these  are  decomposed,  the  products  are  sul- 
phuretted hydrogen  and  other  odorous  derivatives. 

When  the  decomposition  takes  place  spontaneously,  the 
alkaline  reaction  being  maintained,  the  products  are  carbon 
bisulphide  and  traces  of  other  sulphur  derivatives. 

The  mechanical  difficulties  of  handling  viscose  are  largely 
a  question  of  materials,  that  is,  of  materials  having  the 
power  of  resisting  the  attack  of  the  associated  products 
whether  in  the  original  condition  or  under  the  condition  of 
decomposition  by  the  reagents  above  indicated. 

It  would  be  outside  the  scope  of  this  work  to  deal  with 
these  matters  in  detail. 

A  large  number  of  inventions  dealing  with  these  methods 
and  details  have  grouped  themselves  around  the  original 
invention,  which  dates  from  1892.  These  inventions  and 
developments  are  so  numerous  that  they  form  the  subject 
of  a  monograph  of  127  pages,  with  88  pages  additional, 
devoted  to  the  patent  literature.  We  give  the  title  of  this 
work  in  full :  "  Die  Viscose — ihre  Herstellung,  Eigen- 
schaften,  and  Anwendung,"  von  Dr.  B.  M.  Margosches  in 
Brunn.  Leipzig.  L.  A.  Klepzig. 

This  monograph  is  extensive,  and  in  fact  complete,  and 
it  is  therefore  unnecessary  to  duplicate  this  contribution  to 
technical  literature. 

In  the  course  of  discussions  in  this  and  preceding  sections, 
we  have  not  dealt  directly  with  the  commercial  aspects  of 


WOOD   PULP  AND  THE  TEXTILE  INDUSTRIES      249 

the  wood  pulp  industries  nor  with  the  subject  of  their 
money  or  selling  values.  These  involve  questions  of  minute 
detail,  and  a  special  aspect  of  these  industries  outside  the 
scope  of  the  present  work. 

But  we  may  deal  in  a  very  broad  and  general  way  with 
these  values,  as  an  illustration  of  an  important  principle  of 
technology,  that  is,  the  appreciation  of  value  of  a  raw 
material  worked  up  by  the  agencies  of  chemical  reagents, 
coal  and  steam,  and  manual  labour,  into  a  finished 
manufactured  product. 

The  German  language,  we  may  note  in  passing,  provides 
the  apt  term  "  vered(e)lung  "  which  means  literally 
"ennobling,"  for  this  process  of  adding  value  to  raw 
materials  and  the  special  term  connotes  the  general  idea  and 
aim  of  manufacturing  industry.  We  have  to  borrow  a 
Latin  equivalent,  and  this  suggests  that  the  idea  of 
"  appreciation  "  is  somewhat  of  an  exotic. 

However  the  associated  ideas  may  be  expressed  and 
assimilated  the  facts  are  equally  striking  and  interesting, 
and  in  the  case  of  the  cellulose  industries  they  may  be  stated 
in  the  form  of  an  ascending  scale  of  related  values  as 
follows: — 

£    s.    d. 

(a)  1  cubic  metre  of  wood  weighs  400 — 500  kilos. 

and  is  worth  in  the  forest,  say         .         .030 

(b)  Used  as  fuel  it  has  a  "  burning  "  value,  say      060 

(c)  As  mechanical  wood  pulp  it  is  worth,  say    .       076 

(d)  Treated  by  the  bisulphite  or  alkali  process 

it  would  yield  150  kilos,  of  pulp,  say         .      0  15     0 

(e)  Transformed  into  paper  the  pulp  or  cellulose 

is  worth,  say    .         .         .  .         .       1  15     0 


250  WOOD  PULP  AND  ITS  USES 

£    s.    d. 

(f)  Transformed  into   wood  pulp    yarn,   it    is 

worth,  say 250 

(g)  Transformed   into   artificial   silk   or  lustra 

cellulose,  it  is  worth,  say 1        .        .  7  10    0 

These  figures  cannot  be  stated  more  exactly,  that  is, 
represent  actual  selling  values ;  but  fractional  variations 
would  not  affect  the  general  scale  of  values  which  mounts  in 
multiples  from  1  to  50.  Specialists  are  aware  that  these 
achievements  in  "veredlung"  by  no  means  exhaust  the 
possibilities  of  cellulose  technology  and  industry. 

1  This  interesting  industrial  record  we  owe  to  Dr.  0.  Witt  and  Max 
Muller. 


CHAPTER  XI 

SPECIMEN  PAGES — VARIOUS  TYPES  OF  PAPER 

THIS  chapter  embodies  specimen  sheets  of  paper  selected 
as  types,  with  a  description  of  their  characteristics.  The 
selection  is  designed  to  bring  out  the  position  of  wood 
pulps,  in  their  various  forms,  as  staple  paper-making  raw 
material. 

In  establishing  this  position  there  have  been,  of  course, 
the  two  elements  of  competition  :  first,  technical  effect ; 
and  second,  cost. 

As  a  result  of  the  competition,  the  wood  pulps  have 
largely  displaced  cotton,  jute  and  esparto.  The  general 
result  of  their  introduction  has  been  to  cheapen  production, 
with  no  sensible  lowering  of  general  quality. 

It  is  unnecessary  again  to  point  out  that  ground  wood  or 
"  mechanical "  wood  pulp  has  many  undesirable  character- 
istics, and,  of  course,  it  is  rigidly  excluded  from  papers  for 
documents  of  permanent  value. 

But  even  this  "Cinderella"  fibre  has  proved  of  great 
practical  importance  and  utility,  in  enabling  papers  to 
be  produced  at  a  cost  commensurate  with  the  enormous 
demand  for  cheap  publications. 

The  careful  comparison  of  these  papers,  with  attention 
to  the  full  specification  of  characteristics  printed  on  each 
sheet,  will  enable  the  reader  to  draw  his  own  conclusions  as 
to  the  extent  to  which  wood  has  vindicated  its  present 
position  as  of  first-rate  importance. 


SPECIMEN  PAPER.     Xo.  1. 


Trade  Description. 

Heavy  Imitation  Art.     46  Ibs.  Demy  =  480  sheets. 

(.Messrs.  Spalding  &  Hodge.) 

Price  2|d.  per  Ib. 


RESULTS   OF   TEST. 
WEIGHT  OF  REAM. 

Demy  174"  *  22i"  =  480  sheets       46  Ibs: 
Grammes  per  square  metre     ... 

THICKNESS. 

Single  sheet         .........     -0058  ins. 

STRENGTH. 

Tensile  strength  on  strips 
15  mm.  wide  (Leunig's  machine) 
Machine  direction         14  '1  Ibs. 
Cross  direction  9'3  Ibs. 

Mean  tensile  strength  of  paper 

BREAKING  LENGTH    ......... 

BREAKING  WEIGHT  PER  SQ.  MM.  OF 
SECTIONA  L  AREA     ...... 

Loss  OF  STRENGTH  DUE  TO  FOLDING. 
On  folding  4  times  mean  %  loss 
On  folding  12  times  mean  %  loss 

BURSTING  STRAIN. 

Lbs.  per  square  inch  required 
Grammes  per  square  centimetre 


117  Ibs. 
2269  yds. 


51  '3% 
65'0% 


24-0  Ibs. 


171  '1  gins. 


-147  mm. 


5-32  Kilos. 
2073  Metres. 

2413  gms. 


1687  gms. 


Percen 

FIBROUS  C 
Espart 
Sulphi 

tage  of  loading   30 

OMPOSITION. 
0                               8( 

•4% 

>% 
>% 

be  Wood 

2( 

VOLUME  COMPOSITION. 

Grammes  per  c.c. 

Percentage  composition 
by  volume. 

Paper 
1-163 

Fibre 

•809 

Ash 
•354 

Fibre 
53-9 

Ash 
14-2 

Air  space 
31-9 

SPECIMEN  PAPER.    No.  2. 


Trade  Description. 

High-class  Rag  Paper.     26  Ibs.  Demy  =  480  sheets. 

(Messrs.  Wiggins,  Teape  &  Co.) 

Price  7fd.  per  Ib. 


RESULTS  OF  TEST. 

WEIGHT  OF  REAM. 

Demy  17£"  x  22J"  =  480  sheets 
Grammes  per  square  metre     ... 

THICKNESS. 

Single  sheet         

STRENGTH. 

Tensile  strength  on  strips 
15  mm.  wide(Leunig's  machine) 
Machine  direction         18'7  Ibs. 
Cross  direction  12'1  Ibs. 

Mean  tensile  strength  of  paper 

BREAKING  LENGTH    .. 


•0042  ins. 


15-4  Ibs. 
5287  yds. 


BREAKING  WEIGHT  PER  SQ.  MM.  OP 
SECTIONAL  AREA    

Loss  OF  STRENGTH  DUE  TO  FOLDING. 

On  folding  4  times  mean  %  loss        5'8  % 
On  folding  12  times  mean  %  loss      13'6  % 

BURSTING  STRAIN. 

Lbs.  per  square  inch  required     45*5  Ibs. 

Grammes  per  square  centimetre 
ASH. 

Percentage  of  loading 2'6% 

SIZING. 

Percentage  of  gelatine  ...       4-16% 

FIBROUS  COMPOSITION. 

Cotton  ...        100% 


96-7  gms. 


•107  mm. 


7-03  Kilos. 
4830  Metres. 

4379  gms. 


3200  gms. 


VOLUME  COMPOSITION. 

Grammes  per  c.c. 

Percentage  composition 
by  volume. 

Paper 
•904 

Fibre 
•844 

Ash 
•023 

Gela- 
tine 

•037 

Fibre 
56-3 

Ash 
0-9 

Gela- 
tine 

2-7 

Air 
space 

40-1 

SPECIMEN  PAPER.    No.  3. 


Trade  Description. 

Sulphite  Printing.     21  Ibs.  Demy  =  480  sheets. 

(Messrs.  Lepard  &  Smith.) 

Price  2Jd.  per  Ib. 


RESULTS  OF  TEST. 

WEIGHT  OF  REAM. 

Demy  17£"  x  22£"  =  480  sheets        21  Iba. 

Grammes  per  square  metre    ...  78 •!  gins. 

THICKNESS. 

Single  sheet        -0033  ins.       -084  mm. 

STRENGTH. 

Tensile  strength  on  strips 

15  mm.  wide 

Machine  direction  7*4  Ibs. 

Cross  direction  2 '5  Ibs. 

Mean  tensile  strength  of  paper     5'0  Ibs.          2 -27  Kilos. 

BREAKING  LENGTH 2125  yds.      1938  Metres 

BREAKING  WEIGHT  PER  SQ.  MM.  OF 

SECTIONAL  AREA 1800  gms. 

Loss  OF  STRENGTH  DUE  TO  FOLDING. 

On  folding  4  times  mean  loss     34  '0% 

On  folding  12  times  mean  loss      40*0  % 
BURSTING  STRAIN. 

Lbs.  per  square  inch  required        9'5  Ibs. 

Grammes  per  square  centimetre  668  gins. 

ASH. 

Percentage  of  loading 22 -0  % 

FIBROUS  COMPOSITION. 

Sulphite  wood 100% 


VOLUME  COMPOSITION. 

Grammes  per  c.c. 

Percentage  composition 
by  volume. 

Paper 
•929 

Fibre 
•725 

Ash 
•204 

Fibre 
48-3 

Ash 

8-2 

Air  space 
43-5 

SPECIMEN  PAPER.     No.  4. 


Trade  Description. 

Imitation  Art.     22  Ibs.  Demy  ==  480  sheets. 

(Messrs.  Lepard  &  Smiths,  Ltd.) 

Price  2|d.  per  Ib. 


RESULTS   OF  TEST. 

WEIGHT  OF  REAM. 

Demy  17£"  x  2-2£»  =  480  sheets         22  Ibs. 

Grammes  per  square  metre    ...  81'Sgms. 

THICKNESS. 

Single  sheet        -0030  ins.       -076mm. 

STRENGTH. 

Tensile  strength  on  strips 

15  mm.  wide  (Leunig's  machine) 

Machine  direction  9 '4  Ibs. 

Cross  direction  47  Ibs. 

Mean  tensile  strength  of  paper     7'1  Ibs.         3-23  Kilos. 

BREAKING  LENGTH 2880yds.      2633  Metres. 

BREAKING  WEIGHT  PER  SQ.  MM.  OF 

SECTIONAL  AREA    2834  gms. 

Loss  OF  STRENGTH  DUE  TO  FOLDING. 

On  folding  4  times  mean   loss      54  '9  % 

On  folding  12  times  mean  loss      69'0  % 
BURSTING  STRAIN. 

Lbs.  per  square  inch  required      15' 1  Ibs. 

Grammes  per  square  centimetre  1055  gins. 

ASH. 

Percentage  of  loading  ..         ...      24'2  % 
FIBROUS  COMPOSITION. 


Esparto     .  .  . 
Sulphite  wood 

90% 

10% 

VOLUME  COMPOSITION. 

Grammes  per  c.c. 

Percentage  composition 
by  volume. 

Paper 
1-076 

Fibre 
•816 

Ash 
•260 

Fibre 
54-4 

Ash 
10-4 

Air  space 
35-2 

SPECIMEN  PAPER.     No.  5. 


Trade  Description. 

Esparto  Printing.     22  Ibs.  Demy  =  480  sheets. 

(Messrs.  Lepard  &  Smiths,  Ltd.) 

Price  2|d.  per  Ib. 


RESULTS   OF  TEST. 

WEIGHT  OF  REAM. 

Demy  17$"  x  22£"  =  480  sheets        22  Ibs. 

Grammes  per  square  metre    ...  81 '8  gms. 

THICKNESS. 

Single  sheet        -0034  ins.       -086mm. 

STRENGTH. 

Tensile  strength  on  strips 

15  mm.  wide  (Leunig's  machine) 

Machine  direction  9'5  Ibs. 

Cross  direction  5  "3  Ibs. 

Mean  tensile  strength  of  paper     7 '4  Ibs.          3 '37  kilos. 

BREAKING  LENGTH 3002yds.      2745  metres. 

BREAKING  WEIGHT  PER  SQ.  MM.  OF 

SECTIONAL  AREA 2613  gms. 

Loss  OF  STRENGTH  DUE  TO  FOLDING. 

On  folding  4  times  mean  loss     32 -4  % 

On  folding  12  times  mean  loss      44 -(5  % 
BURSTING  STRAIN. 

Lbs.  per  square  inch  required      17'2  Ibs. 

Grammes  per  square  centimetre  1198  gms. 

ASH. 

Percentage  of  loading 17'0% 

FIBROUS  COMPOSITION. 

Esparto     80% 

Sulphite  wood     20% 


VOLUME  COMPOSITION. 

Grammes  per  c.c. 

Percentage  con 
by  volum 

position 
e. 

Paper 
•952 

Fibre 

•790 

Ash 
•1(52 

Fibre 
527 

Ash 

6'5 

Air  space 
40-8 

SPECIMEN  PAPER.    No. 


Trade  Description. 

High-class  Art  Paper.     41  Ibs.  Demy  —  480  sheets. 
Prices  on  application  to  Messrs.  C.  Morgan  &  Co. 

RESULTS  OF  TEST. 
WEIGHT  OF  REAM. 

Demy  17*"  x  22£"  =  480  sheets       41  Ibs. 

Grammes  per  square  metre     ...  152'5  gms. 

THICKNESS. 

Single  Sheet        

STRENGTH. 

Tensile  strength  on  strips 

15  mm.  wide  (Leunig's  machine) 

Machine  direction         i:>-8  Ibs. 

Cross  direction  7 '4  Ibs. 

Mean  tensile  strength  of  paper     10'6  Ibs. 

BREAKING  LENGTH 2306  yds. 


•0052  ins.         '132  mm. 


BREAKING  WEIGHT  PER  SQ.  MM.  OF 
SECTIONAL  AREA    

Loss  OF  STRENGTH  DUE  TO  FOLDING. 

On  folding  4  times  mean  %  loss        49'1% 

On  folding  12  times  mean  %  loss       63-2% 
BURSTING  STRAIN. 

Lbs    per  square  inch  required     23'3  Ibs. 

Grammes  per  square  centimetre 
ASH. 

Percentage  of  loading 29'0% 

SIZING. 

Percentage  of  gelatine 5-43% 

FIBROUS  COMPOSITION. 


4-85  Kilos. 
2114  Metres. 

2438  gms. 


1638  gms. 


Esparto     
Sulphite  Wood    

45% 
55% 

VOLUME  COMPOSITION. 

Grammes  per  c.c. 

Percentage  composition 
by  volume. 

Paper 
1-152 

Fibre 

•755 

Ash 
•334 

Gela- 
tine 

•063 

Fibre 
50-3 

Ash 
13-4 

Gela-  j    Air 
tine     space 

4-7         31-6 

SPECIMEN  PAPKR.     No.  7. 


Trade  Description. 

Common  Art  Paper.     38  Ibs.  Demy  =  480  sheets. 
(Messrs.  Lepard  &  Smiths.) 
Price  2|d.  per  Ib. 


RESULTS  OF  TEST. 
WEIGHT  OF  REAM. 

Demy  17J"  x  22£"  =  480  sheets       38  Ibs. 

Grammes  per  square  metre    ... 
THICKNESS. 

Single  sheet        -0053  ins. 

STRENGTH. 

Tensile  strength  on  strips 

15  mm.  wide  (Leunig's  machine) 

Machine  direction         11 -8  Ibs. 

Cross  direction  4-8  Ibs. 

Mean  tensile  strength  of  paper      8 '3  Ibs. 

BREAKING  LENGTH  ... 


BREAKING  WEIGHT  PER  SQ.  MM.  OF 
SECTIONAL  AREA 

Loss  OF  STRENGTH  DUE  TO  FOLDING. 
On  folding  4  times  mean  %  loss 
On  folding  12  times  mean  %  loss 

BURSTING  STRAIN. 

Lbs.  per  square  inch  required 
Grammes  per  square  centimetre 

ASH. 

Percentage  of  loading 

SIZING. 

Percentage  of  gelatine 

FIBROUS  COMPOSITION. 


1950  yds 


41-0% 
48-2% 

18-2  Ibs. 


28-3% 


141'4gms. 
•135  mm. 


3-76  Kilos. 
1778  Metres. 

1858  gms. 


1275  gms. 


Sulphite  Wood   
Mechanical  Wood         

90% 
10% 

VOLUME  COMPOSITION. 

Grammes 

per  c.c. 

Percentage  composition 
by  volume. 

Paper 
1-047 

Fibre 
•710 

Ash 
•296 

Gela- 
tine. 

•041 

Fibre 
47-3 

Ash 
11-8 

Gela- 
tine. 

3-0 

Air 

space. 

37-9 

SPECIMEN  PAPER.     Xo.  8. 


Trade  Description. 

Common  News.    14  Ibs.  Demy  =  480  sheets. 
Prices  on  application  to  Messrs.  C.  Morgan  &  Co. 


RESULTS  OP  TEST. 
WEIGHT  OF  REAM. 

Demy  17J"  x  22^"  =  480  sheets       14  Ibs. 
Grammes  per  square  metre    ... 

THICKNESS. 

Single  sheet       .........     -0041  ins. 

STRENGTH. 

Tensile  strength  on  strips 

15  mm.  wide  (Leunig's  machine) 

Machine  direction          5'5  Ibs. 

Cross  direction  2  '4  Ibs. 

Mean  tensile  strength  of  paper      4'0  Ibs. 

BREAKING  LENGTH   .........    2550  yds. 

BREAKING  WEIGHT  OF  SQ.  MM.  OF 
SECTIONAL  AREA  ...... 

Loss  OF  STRENGTH  DUE  TO  FOLDING. 

On  folding  4  times  mean  %  loss       10'0% 
On  folding  12  times  mean  %  loss       20'0% 

BURSTING  STRAIN. 

Lbs.  per  square  inch  required      8'1  Ibs. 
Grammes  per  square  centimetre 

ASH. 

Percentage  of  loading  ......        4*2% 

FIBROUS  COMPOSITION. 


52-1  gms. 


-104mm. 


1  -81  Kilos. 
2324  Metres. 


gms. 


569  gms. 


Sulphite  wood    10% 
Mechanical  wood         90% 

VOLUME  COMPOSITION. 

Grammes  per  c.c. 

Percentage  composition 
by  volume. 

Paper 
•500 

Fibre 
•479 

Ash 
•021 

Fibre 
31-9 

Ash 
0-84 

Air  space 
67-S 

SPECIMEN  PAPER.    No.  9. 


Trade  Description. 

High-class  News.    18  Ibs.  Demy  =  480  sheets. 
Prices  on  application  to  Messrs.  C.  Morgan  &  Co. 


RESULTS  OF  TEST. 
WEIGHT  OF  REAM. 

Demy  17i"  x  22J"  =  480  sheets       18  Ibs. 
Grammes  per  square  metre    ... 

THICKNESS. 

Single  sheet       '0045  ins. 

STRENGTH 

Tensile  strength  on  strips 

15  mm.  wide  (Leunig's  machine) 

Machine  direction          6'3  Ibs. 

Cross  direction  4'1  Ibs. 

Mean  tensile  strength  of  paper      5-2  Ibs. 

BREAKING  LENGTH  .., 


BREAKING  WEIGHT  PER  SQ.  MM.  OF 

SECTIONAL  AREA  ...... 

Loss  OF  STRENGTH  DUE  TO  FOLDING. 
On  folding  4  times  mean  %  loss 
On  folding  12  times  mean  %  loss 

BURSTING  STRAIN. 

Lbs.  per  square  inch  required 
Grammes  per  square  centimetre 

ASH. 

Percentage  of  loading  ...... 

FIBROUS  COMPOSITION. 


2578  yds. 


15  '4% 
19"2% 


11  '4  Ibs. 


3-3% 


67'0gms. 


•114  mm. 


2-36  Kilos. 
2350  Metres. 

1378  gms. 


Sulphite  Wood  80% 
Mechanical  Wood          20% 

VOLUME  COMPOSITION. 

Grammes  per  c.c. 

Percentage  composition 
by  volume. 

Paper 

•587 

Fibre 
•568 

Ash 
•019 

Fibre 
37-9 

Ash 
0-8 

Air  space 
61-3 

SPECIMEN  PAPER.    No.  10. 


Trade  Description. 

Bulking  Antique  Wove  Printing.    18  Ibs.  Demy  =  480  sheets. 
Prices  on  application  to  Messrs.  C.  Morgan  &  Co. 


RESULTS  OF  TEST. 
WEIGHT  OF  REAM. 

Demy  17£"  x  22J"  =  480  sheets       18  Ibs. 
Grammes  per  square  metre    ... 

THICKNESS. 

Single  sheet        '0066  ins. 

STRENGTH. 

Tensile  strength  on  strips 

15  mm.  wide(Leunig's  machine) 

Machine  direction          77  Ibs. 

Cross  direction  4'2  Ibs. 

Mean  tensile  strength  of  paper      6'0  Ibs. 

BREAKING  LENGTH 2975  yds. 

BREAKING  WEIGHT  PER  SQ.  MM.  OF 
SECTIONAL  AREA 

Loss  OF  STRENGTH  DUE  TO  FOLDING. 
On  folding  4  times  mean  %  loss 
On  folding  12  times  mean  %  loss 

BURSTING  STRAIN. 

Lbs.  per  square  inch  required 
Grammes  per  square  centimetre 


35-0% 
41-7% 

13-1  Ibs. 


Percentage  of  loading 

FIBROUS  COMPOSITION. 

Esparto    

Sulphite  Wood   ... 


7-5% 


5% 


67-0 


•168  mm. 


2-72  Kilos. 
2710  Metres. 

1081  gms. 


914  gms. 


VOLUME  COMPOSITION. 

Grammes  per  c.c. 

Percentage  composition 
by  volume. 

Paper 
•400 

Fibre 
'370 

Ash 
•030 

Fibre 

24-7 

Ash 
1-2 

Air  space 
74-1 

SPECIMEN  PAPER.    No.  11. 


Trade  Description. 

Cartridge.    29  Ibs.  Demy  =  480  sheets. 

(Messrs.  Lepard  &  Smiths.) 

Price  2Jd.  per  Ib. 

RESULTS  OF  TEST. 
WEIGHT  OF  REAM. 

Demy  17$"  x  22$"  =  480  sheets       29  Ibs. 

Grammes  per  square  metre     ...  107*9  gms. 

THICKNESS. 

Single  sheet        -0055  ins.        -140  mm. 

STRENGTH. 

Tensile  strength  on  strips 

15  mm.  wide  (Leunig's  machine) 

Machine  direction         14-5  Ibs. 

Cross  direction  6*8  Ibs. 

Mean  tensile  strength  of  paper     10'2  Ibs.        4-63  Kilos. 

BREAKING  LENGTH 8189  yds.     2865  Metres. 

BREAKING  WEIGHT  PER  SQ.  MM.  OF 

SECTIONAL  AREA 2207  gms 

Loss  OF  STRENGTH  DUE  TO  FOLDING. 

On  folding  4  times  mean  %  loss       30-4% 
On  folding  12  timea  mean  %  loss       40'  2% 

BURSTING  STRAIN. 

Lbs.  per  square  inch  required     19'8  Ibs. 

Grammes  per  square  centimetre  1891  gins. 

ASH. 

Percentage  of  loading 9-5% 

FIBROUS  COMPOSITION. 


Sulphite  wood    99% 
Mechanical  wood          1% 

VOLUMK  COMPOSITION. 

Grammes  per  c.c. 

Percentage  composition 
by  volume. 

Paper 
•771 

Fibre 
•698 

Ash 
•073 

Fibre 
4«'5 

Ash 
2-9 

Air  space 
50-6 

BIBLIOGRAPHY 


TITLE  AND  AUTHOR. 

Beitrage  zur  Kenntnis  der  Che- 

niische    zusammensetzung  des 

Fichtenholzes.         P.      Klason. 

Berlin,  1911 :  Borntraeger. 
Cellulose,  1895. 

Researches  on  Cellulose,  I.,  1901. 
Researches  on  Cellulose,  II.,  1906. 

Cross  &  Bevan. 
Chemistry     of     Papermaking. 

Griffin   &   Little.     New  York, 

1894:  Lockwood. 
Die  Chemie  der  Cellulose.     Carl. 
.G.    Schwalbe.      Berlin,    1910: 

Borntraeger. 
Die  Cellulose  Fabrikation.     Max 

Schubert.     Berlin,  1906. 
Etudes   sur  les  Fibres  Vegetales 

textiles.     M.  Vetillart.     Paris, 

1876. 


Introduction  to  Vegetable  Phy- 
siology. J.  Reynolds  Green. 
1900. 

Paper-maker's  Pocket  Book.  J. 
Beveridge. 

Papierprufung.     Herzberg.     3rd 

edition.     Berlin,  1906. 
Pflanzen  Faser.     Hugo   Mueller. 

Reports     Vienna     Exhibition, 

1873. 


CHARACTER  OF  SUBJECT-MATTER. 
Theoretical  investigation  of  con- 
stitution of  pine  wood. 


Systematic  account  of  the  chem- 
istry of  cellulose  and  deriva- 
tives, and  special  accounts  of 
researches  to  date. 

Modern  account  of  wood  pulp 
processes. 

A  compilation  on  various  works 
on  cellulose. 

A  practical  text-book  dealing  with 
wood  pulp  processes. 

A  standard  book  of  reference  on 
vegetable  fibres,  dealing  with 
minute  structure  and  correla- 
tion of  microscopic  charac- 
teristics with  industrial  uses. 

A  standard  text-book  of  plant 
physiology. 

Tabulated  constants  and  numeri- 
cal statistics  incidental  to 
manufacturers. 


Original  investigations  on  vege- 
table fibres. 


264 


WOOD  PULP  AND  ITS  USES 


CHARACTER  OF  SUBJECT-MATTER. 

An  excellent  book,  dealing  with 

plant  morphology. 
Thorough  manufacturing  details. 


Engineering  details. 

Original  collection  of  statistics. 


TITLE  AND  AUTHOR. 

Plant  Structures.    Coulter.    New 

York,  1900. 
Praktischer  Handbuch  der  Papier- 

fabrikation.    Hoffman.    Berlin, 

1897. 
Technologic  der  Fabrikant.     E. 

Kirchner.     Biberach,  1905-7. 
The  Paper  Trade.     A.  D.  Spicer. 

London,  1907. 
Die    Viskose     ihre     Herstellung 

Eigenschaften     und      Anwen- 

dung.      Leipsic,   1906.      Mar- 

gosches. 


ARTICLES. 

"  Paper  "  in  Spon's  Encylopsedia  of  Useful  Arts. 

"Cellulose,"    "Paper."      Thorpe's   Dictionary   of  Chemistry. 


JOURNALS. 
Papermaker. 
Papermaking. 
Paper  Trade  Review. 
Paper,  Box,  and  Bag  Maker. 
Paper  Trade  Journal.     New  York. 
Papierzeitung.     Berlin. 
Papier  Fabrikant. 
Wochenblatt  fuer  Papierfabrikation.    Biberach. 


INDEX 


ACETATES  of  cellulose,  36,  48 
bibliography,  240 
cost  of  production,  238 
solvents,  238 

Aceto-sulphates  of  cellulose,  49 

Acid -sulphuric  esters  of  cellulose, 
48 

Afforestation,  79—85 

Alcohol     from    waste     sulphite 
liquor,  128 

Alkali-cellulose,  50 

Alkalis,  action  upon  cellulose,  52 
sawdust,  199 

Angiosperms,  4 

Aniline  sulphate,  114 

Annual  rings,  19 

Aromatic  bases,  70 

Artificial  silk,  41 

Assimilating  organs,  4 
tissue,  16 

Autoxidation,  29 

B. 

BARKING  machine,  96 

Bast,  18 

Beating,  184 

Beech  wood,  29 

Benzoates  of  cellulose,  36,  49 


Beveridge,  134 

Birdseye  grain,  24 

Bisulphites,  58 

Bleaching  of  wood  pulp,  147,  152, 

173,  174 

powder      liquors, 
analysis,  147 
consumption, 

153—162 
effect   of  keep- 
ing, 148 
residual,  149 
strength,  147 

Board  machines,  191,  192 

Box-making,  193 

Breaking  length,  40 

Breast  roll,  187 

Brown  wood  pulp,  109 

Burr,  24 

C. 

CALLUS  plate,  18 

Calorific  value  of  wood,  27 

Cambium,  20 

Canadian    Forestry    Convention, 

82 

Castner-Kellner  system,  175 
Cell,  9 

Celluloid,  235 
Cellulose,  29 

acetates,  36,  48,  238,  240 


266 


INDEX 


Cellulose, 

acetates,  bibliography,  240 

aceto-sulphates,  49 

acid-sulphuric  esters,  48 

action  of  alkalis,  52 

benzoates,  36,  49 

compound,  55 

constitution,  46 

decomposition,  54 

denitration,  242 

double  salts,  36 

esters,  36,  45,  47,  234,  242 

group,  55 

mixed  esters,  50 

nitrates,  36,  234,  242 

oxidation,  52,  53 

relative   values    of    different 
forms,  249 

solvents,  47 

special  industries,  234 
Chemical  wood  pulp,  28,  120 

history,  91 

list  of  inventions,  28,  120 
Chlorine,  58,  116,  165 
Chromic  acid,  53 
Claviez  system,  221 
Cold  ground  pulp,  97 
Collateral  bundles,  21 
Collenchyma,  16 
Colloids,  33 
Comparison  of  sulphite  and  soda 

wood  papers,  135 — 140 
Composition  of   sulphate  liquor, 

140 
waste      sulphite 

liquor,  124 

Compound  celluloses,  55 
Concentrator,  143 
Conducting  tissue,  13 
Constitution  of  cellulose,  46 
Cork,  15 
Cortex,  15 


Cost  of  afforestation,  83 
Couch  roll,  187 
Cross  and  Bevan,  41 
Crystalloids,  33 


D. 

DENITRATION  of  cellulose,  242 
Densities  of  various  woods,  25 
Destructive  distillation,  54,  202 
Dextion,  125 
Dicotyledonous   stem    structure, 

18 
Dimethylparaphenylene  diamine, 

70,  114 
Dorenfeldt,  126 


E. 


ECONOMICAL  bleaching  conditions, 

144 

Eibel  system,  188 
Ekman  and  Fry,  94 
Elasticity,  40 
Electrical  units,  163—165 
Electrolytes,  34,  165 
Electrolytic  bleaching,  162 
Epidermis,  15 
Exogenous  stem,  19 
Explosives,  239 
Extensibility,  40 


F. 


FELTING,  187 

Ferments,  action  upon  cellulose, 

53 

Fern,  structural  features,  3 
Ferric-ferricyanide,  68,  114 


INDEX 


267 


Fibres,  11 

length  of  various,  215 
Films,  43 

photographic,  237 
Forestry,  78 
Fossil  resins,  75 
Fourdrinier  paper  machine,  187 
Furfural,  55,  61 

G. 

GELATINE,  33 
Ginning  process,  219 
Grain,  22 
Grinder,  98 
Gun-cotton,  234 
Gymnosperms,  4 

H. 

HAAS  and  Oettel  apparatus,  166 

Hardness  of  various  woods,  26 

Hargreaves-Bird  process,  175 

Heart  wood,  20 

Hemicellulose,  56 

History  of  chemical  pulp,  91 

mechanical  pulp,  90 

Hoffmann,  124,  225 

Hollander,  185 

Hot  ground  pulp,  97 

Houghton,  92 

Humidity   of   atmosphere,  effect 
upon  various  pulps,  213 

Hydriodic     acid,      action     upon 
cellulose,  63 

Hydrobromic    acid,  action   upon 
cellulose,  51 

Hydrochloric   acid,    action   upon 
cellulose,  52 

Hydroxy  furfurals,  70 

Hypochlorites,  action  upon  cellu- 
lose, 52 
W.P. 


J. 

JORDAN  refiner,  187 
Jute  fibre,  29 

xanthogenic  acid,  68 

K. 

KELLNER-TURK  system,  222 
Kirschner,  100—105 
Kraft  papers,  134 
Kron  system,  226 


LlGNlFICATION,  29 

Lignified  vessels,  25 
Ligno-cellulose,  30,  56—64 

bleaching,  65—67 

esters,  65 

photochemical     phenomena, 

71 
Lignone,  30,  57—64 

action  of  bisulphites,  58 
chlorine,  58,  116 

constitution,  66 

effect  on  chemical  reactivity, 
68 

sulphonates,  65,  124 
Lignorosin,  127 
Lustra-cellulose,  42 

M. 

MAGNESIUM  hypochlorite,  166 
Manufacture   of    chemical    wood 

pulp,  120 
mechanical  wood, 

96 

Marshall  refiner,  187 
Measurement  of  timber,  equiva- 
lent table,  88 

8 


268 


INDEX 


Mechanical  tissue,  13,  16 

wood  pulp,  27,  96 
determination    in 
papers,  111— 119 
manufacture,  96 
output   under 
varying    condi- 
tions, 100—105 
Medulla,  19 
Medullary  rays,  19,  24 
Meristematic  tissue,  20 
Mestome,  13 
Methoxyl,  63 
Methyl    groups,    percentage     in 

various  woods,  64 
Metrical  yarn  numbers,  231 
Micro-chemical  reactions  of  fibres, 

113 

Microscopic  analysis,  112 
Mixed  esters  of  cellulose,  49,  50 
Monocotyledoiious    stem    struc- 
ture, 21,  22 
Multiple  effect  evaporator,  138 

N. 

"  NEWS"  and  Printings,  178 

mill,  economy  in  work- 
ing, 180 
Newspaper,  composition,  180 

improvements          in 

manufacture,  183 
Nitrates  of  cellulose,  36 
Nitric  acid,  60 


O. 

OSMGSIS,  34 
Oxalic  acid,  200 
Oxidants,  52 
Oxycellulose,  53 


P. 


PAPER  pulp  yarns,  220 

Para-abietic  acid,  22 

Parenchyma,  12 

Patent  Spinnerei,  228 

Pentosan,  62 

Permanganates,       action      upon 

cellulose,  52 
Phenols,  69,  114 
Phloem,  18 

Phloro-glucinol,  69,  114 
Photo-chemical  phenomena,  71 
Photographic  films,  237 
Photosynthesis,  6 
Physical  properties  of  woods,  25 
Pinchot,  81 
Pith,  19 

flecks,  25 

rays,  19 

Pollution  of  streams,  129 
Porion  evaporator,  137 
Power,  181 
Printing  papers,  70 
Producer  gas  from  wood,  200 

Q. 

QUICK  cook  process,  121 

E. 

EEACTIONS  of  decomposition,  51 
Kefiners,  187 

Kelation  of  yarn  to  paper,  218 
Kesidual  bleach  liquors,  149 
Russell,  29,  71 

S. 

SAP  wood,  20 
Saponification,  48 
Sawdust  uses,  199 


INDEX 


269 


Schimmel,  O.,  &  Co.,  223 

Schuckert's  electrolyser,  172 

Sclerenchyiua,  16 

Screening,  105 

Secretionary  products  of  plants, 

25 

Sheathing  tissue,  16 
Siemens   &  Halske   electrolyser, 

168 

Sieve  tube,  18 
Silvalin  yarns,  226 
Slowcook  process,  122 
Soda  process,  131 

recovery,  136 
Sodium  hypochlorite,  163 
Solvents  of  cellulose,  47 
Sources  of  supply,  76 
Spermatophytes,  3 
Spinning  of  textile  yarns,  217 
Starch,  32 
Steamed  wood,  109 
Stele,  15 
Stem      structure,      contrast      of 

inonocotyl  and  dicotyl,  14 
Stereome,  13 
Strehlenert,  41 

Strength  of  various  woods,  26 
wood  pulp 

yarns,  228 
Sugars,  34 
Sulphate  liquor,  analysis,  140 

process,  139 
Sulphite  liquor,  122 

process,  121 
Sulpho-carbonates,  39 
Sulphuric  acid,  51 

T. 

• 

TEMPERLEY,  150 
Tenacity,  40 
Tensile  strength,  40 


Testing  wood  pulp  for  moisture, 

206 

Tetmayer,  26 
Textile  industries,  215 

yarns  from  paper,  220 
Tilghman,  92 
Tintometer,  161 
Tower  system  of  bleaching,  142 
Trachea,  18 
Tracheids,  18 


V. 

VASCULAR  tissue,  14 
Vessels,  11 

Viscose,  39,  43,  242—249 
spinning,  245 — 247 


W. 

WASHING  and  finishing,  130 
Waste  sulphite  liquors,  123 
composition,  124 
sizing  products,  125 
Wedge  method  of  testing  pulp, 

209 

Wet  press  machine,  108 
Wood,  18 

calorific  value,  27 
composition,  120 
digestion  in  water,  109 
standards    of    measurement, 

85 

Wood  pulp  bleaching,  141 
boards,  190 
chemical,  28,  120 

list  of  inventions, 

95 
imports,  176 


270 


INDEX 


Wood  pulp,  mechanical,    27,    96, 

100—105, 111—119 

production  in  various 

countries,  77—79 
sources  of  supply,  76 
trees,  89 
yarns,  220 

cost   of    produc- 
tion, 229 
physical  proper- 
ties, 230 
strength,  228 


Wood  waste,  utilisation,  198 
wool,  199 

X. 

XANTHOGENIC  ester   of  cellulose, 
39,  43, 
242,  243 
jute,  68 
Xylem,  18 
Xylolin,  222 
Xylonite,  235 


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THE    "WESTMINSTER"    SERIES 

Coal.  By  JAMES  TONGE,  M.I.M.E.,  F.G.S.,  etc.  (Lecturer 
on  Mining  at  Victoria  University,  Manchester).  With 
46  Illustrations,  many  of  them  showing  the  Fossils  found 
in  the  Coal  Measures. 

LIST  OF  CONTENTS  :  History.  Occurrence.  Mode  of  Formation 
of  Coal  Seams.  Fossils  of  the  Coal  Measures.  Botany  of  the 
Coal-Measure  Plants.  Coalfields  of  the  British  Isles.  Foreign 
Coalfields.  The  Classification  of  Coals.  The  Valuation  of  Coal. 
Foreign  Coals  and  their  Values.  Uses  of  Coal.  The  Production 
of  Heat  from  Coal.  Waste  of  Coal.  The  Preparation  of  Coal 
for  the  Market.  Coaling  Stations  of  the  World.  Index. 

This  book  on  a  momentous  subject  is  provided  for  the  general 
reader  who  wishes  accurate  knowledge  of  Coal,  its  origin,  position 
and  extent,  and  its  economical  utilization  and  application. 

Iron  and  Steel    By  J.  H.  STANSBIE,  B.Sc.  (Lond.),  F.I.C. 

With  86  Illustrations. 

LIST  OF  CONTENTS  :  Introductory.  Iron  Ores.  Combustible  and 
other  materials  used  in  Iron  and  Steel  Manufacture.  Primitive 
Methods  of  Iron  and  Steel  Production.  Pig  Iron  and  its  Manu- 
facture. The  Refining  of  Pig  Iron  in  Small  Charges.  Crucible 
and  Weld  Steel.  The  Bessemer  Process.  The  Open  Hearth 
Process.  Mechanical  Treatment  of  Iron  and  Steel.  Physical 
and  Mechanical  Properties  of  Iron  and  Steel.  Iron  and  Steel 
under  the  Microscope.  Heat  Treatment  of  Iron  and  Steel.  Elec- 
tric Smelting.  Special  Steels.  Index. 

The  aim  of  this  book  is  to  give  a  comprehensive  view  of  the  modern 
aspects  of  iron  and  steel,  together  with  a  sufficient  account  of  its  his- 
tory to  enable  the  reader  to  follow  its  march  of  progress.  The  methods 
of  producing  varieties  of  the  metal  suitable  to  the  requirements  of 
the  engineer,  foundryman  and  mechanician  are  described  so  that  the 
worker  may  learn  the  history  of  the  material  he  is  handling. 

Natural  Sources  of  Power.    By  ROBERT  S.  BALL,  B.Sc., 

A.M.Inst.C.E.  With  104  Diagrams  and  Illustrations. 
CONTENTS  :  Preface.  Units  with  Metric  Equivalents  and  Abbre- 
viations. Length  and  Distance.  Surface  and  Area.  Volumes. 
Weights  or  Measures.  Pressures.  Linear  Velocities,  Angular 
Velocities,  Acceleration.  Energy.  Power.  Introductory 
Water  Power  and  Methods  of  Measuring.  Application  of  Water 
Power  to  the  Propulsion  of  Machinery.  The  Hydraulic  Turbine. 
Various  Types  of  Turbine.  Construction  of  Water  Power  Plants. 
Water  Power  Installations.  The  Regulation  of  Turbines.  Wind 
Pressure,  Velocity,  and  Methods  of  Measuring.  The  Application 
of  Wind  Power  to  Industry.  The  Modern  Windmill.  Con- 
structional Details.  Power  of  Modern  Windmills.  Appendices 
A,B,C  Index. 
Two  departments  of  Engineering  and  their  applications  to  industry 

form  the  subject  of  this  volume  :    the  "  natural  "  sources  of  water 

(    2    ) 


THE     '  WESTMINSTER  "    SERIES 

and  wind  power  which  supply  mechanical  energy  without  any  inter- 
mediate stage  of  transformation.  Most  people  will  be  surprised  at 
the  extent  to  which  these  natural  power  producers  are  used.  The 
widespread  application  of  water  power  is  generally  known,  but  it  is 
interesting  to  learn  that  the  demand  for  windmills  was  never  so  great 
as  it  is  to-day,  and  there  are  signs  of  abnormal  expansion  in  the  direc- 
tion of  their  useful  application  in  the  great  agricultural  countries  of 
the  world.  Though  primarily  of  importance  to  the  engineer,  this  work 
will  be  of  great  interest  to  every  manufacturer  who  in  economizing 
his  means  of  power  production  can  take  the  natural  forces  that  lie 
to  his  hand  and  harness  them  in  his  service.  The  author  is  the  son 
of  Sir  Robert  Ball,  the  eminent  mathematician  and  astronomer. 

Liquid  and  Gaseous  Fuels,  and  the  Part  they  play 
in  Modern  Power  Production.  By  Professor 
VIVIAN  B.  LEWES,  F.I.C.,  F.C.S.,  Prof,  of  Chemistry, 
Royal  Naval  College,  Greenwich.  With  54  Illustrations. 

LIST  OF  CONTENTS  :  Lavoisier's  Discovery  of  the  Nature  of  Com- 
bustion, etc.  The  Cycle  of  Animal  and  Vegetable  Life.  Method 
of  determining  Calorific  Value.  The  Discovery  of  Petroleum 
in  America.  Oil  Lamps,  etc.  The  History  of  Coal  Gas.  Calorific 
Value  of  Coal  Gas  and  its  Constituents.  The  History  of  Water 
Gas.  Incomplete  Combustion.  Comparison  of  the  Thermal 
Values  of  our  Fuels,  etc.  Appendix.  Bibliography.  Index. 

The  subject  of  this  book  has,  during  the  last  decade,  assumed  such 
importance  that  it  is  hoped  this  account  of  the  history  and  develop- 
ment of  the  use  of  various  forms  of  combustible  liquids  and  gases 
for  the  generation  of  energy  may  do  some  service  in  its  advancement. 

Electric  Power  and  Traction*  By  F.  H.  DAVIES, 
A.M.I.E.E.  With  66  Illustrations. 

LIST  OF  CONTENTS  :  Introduction.  The  Generation  and  Distri- 
bution of  Power.  The  Electric  Motor.  The  Application  of 
Electric  Power.  Electric  Power  in  Collieries.  Electric  Power 
in  Engineering  Workshops.  Electric  Power  in  Textile  Factories. 
Electric  Power  in  the  Printing  Trade.  Electric  Power  at  Sea. 
Electric  Power  on  Canals.  Electric  Traction.  The  Overhead 
System  and  Track  Work.  The  Conduit  System.  The  Surface 
Contact  System.  Car  Building  and  Equipment.  Electric  Rail- 
ways. Glossary.  Index. 

The  majority  of  the  allied  trades  that  cluster  round  the  business  of 
electrical  engineering  are  connected  in  some  way  or  other  with  its  power 
and  traction  branches.  To  members  of  such  trades  and  callings,  to 
whom  some  knowledge  of  applied  electrical  engineering  is  desirable 
if  not  strictly  essential,  the  book  is  particularly  intended  to  appeal. 
It  deals  almost  entirely  with  practical  matters,  and  enters  to  some 
extent  into  those  commercial  considerations  which  in  the  long  run 
must  overrule  all  others. 

(  3  ) 


THE    "WESTMINSTER"    SERIES 

Town    Gas   and  its  Uses  for  the  Production  of 
Light,  Heat,  and  Motive  Power,    By  W.  H.  Y. 

WEBBER,  C.E.     With  71  Illustrations. 

LIST  OF  CONTENTS  :  The  Nature  and  Properties  of  Town  Gas.  The 
History  and  Manufacture  of  Town  Gas.  The  Bye-Products  of 
Coal  Gas  Manufacture.  Gas  Lights  and  Lighting.  Practical 
Gas  Lighting.  The  Cost  of  Gas  Lighting.  Heating  and  Warm- 
ing by  Gas.  Cooking  by  Gas.  The  Healthfulness  and  Safety 
of  Gas  in  all  its  uses.  Town  Gas  for  Power  Generation,  including 
Private  Electricity  Supply.  The  Legal  Relations  of  Gas  Sup- 
pliers, Consumers,  and  the  Public.  Index. 

The  "country,"  as  opposed  to  the  "town,"  has  been  denned ~as 
"  the  parts  beyond  the  gas  lamps."  This  book  provides  accurate 
knowledge  regarding  the  manufacture  and  supply  of  town  gas  and  its 
uses  for  domestic  and  industrial  purposes.  Few  people  realize  the 
extent  to  which  this  great  industry  can  be  utilized.  The  author  has 
produced  a  volume  which  will  instruct  and  interest  the  generally  well 
informed  but  not  technically  instructed  reader. 

Electro-Metallurgy.    By  J.  B.  C.  KERSHAW,  F.I.C.    With 
61  Illustrations. 

CONTENTS  :  Introduction  and  Historical  Survey.  Aluminium. 
Production.  Details  of  Processes  and  Works.  Costs.  Utiliza- 
tion. Future  of  the  Metal.  Bullion  and  Gold.  Silver  Refining 
Process.  Gold  Refining  Processes.  Gold  Extraction  Processes. 
Calcium  Carbide  and  Acetylene  Gas.  The  Carbide  Furnace  and 
Process.  Production.  Utilization.  Carborundum.  Details  of 
Manufacture.  Properties  and  Uses.  Copper.  Copper  Refin- 
ing. Descriptions  of  Refineries.  Costs.  Properties  and  Utiliza- 
tion. The  Elmore  and  similar  Processes.  Electrolytic  Extrac- 
tion Processes.  Electro-Metallurgical  Concentration  Processes. 
Ferro-alloys.  Descriptions  of  Works.  Utilization.  Glass  and 
Quartz  Glass.  Graphite.  Details  of  Process.  Utilization.  Iron 
and  Steel.  Descriptions  of  Furnaces  and  Processes.  Yields  and 
Costs.  Comparative  Costs.  Lead.  The  Salom  Process.  The  Betts 
Refining  Process.  The  Betts  Reduction  Process.  White  Lead  Pro- 
cesses. Miscellaneous  Products.  Calcium.  Carbon  Bisulphide. 
Carbon  Tetra-Chloride.  Diamantine.  Magnesium.  Phosphorus. 
Silicon  and  its  Compounds.  Nickel.  Wet  Processes.  Dry 
Processes.  Sodium.  Descriptions  of  Cells  and  Processes.  Tin. 
Alkaline  Processes  for  Tin  Stripping.  Acid  Processes  for  Tin 
Stripping.  Salt  Processes  for  Tin  Stripping.  Zinc.  Wet  Pro- 
cesses. Dry  Processes.  Electro-Thermal  Processes.  Electro- 
Galvanizing.  Glossary.  Name  Index. 

The  subject  of  this  volume,  the  branch  of  metallurgy  which  deals 
with  the  extraction  and  refining  of  metals  by  aid  of  electricity,  is 
becoming  of  great  importance.  The  author  gives  a  brief  and  clear 
account  of  the  industrial  developments  of  electro-metallurgy,  in  lan- 
guage that  can  be  understood  by  those  whose  acquaintance  with  either 

(  4  ) 


THE     '  WESTMINSTER  "    SERIES 

chemical  or  electrical  science  may  be  but  slight.  It  is  a  thoroughly 
practical  work  descriptive  of  apparatus  and  processes,  and  commends 
itself  to  all  practical  men  engaged  in  metallurgical  operations,  as  well 
as  to  business  men,  financiers,  and  investors. 

Radio-Telegraphy*  By  C.  C.  F.  MONCKTON,  M.I.E.E. 
With  173  Diagrams  and  Illustrations. 

CONTENTS  :  Preface.  Electric  Phenomena.  Electric  Vibrations. 
Electro-Magnetic  Waves.  Modified  Hertz  Waves  used  in  Radio- 
Telegraphy.  Apparatus  used  for  Charging  the  Oscillator.  The 
Electric  Oscillator  :  Methods  of  Arrangement,  Practical  Details. 
The  Receiver :  Methods  of  Arrangement,  The  Detecting  Ap- 
paratus, and  other  details.  Measurements  in  Radio-Telegraphy. 
The  Experimental  Station  at  Elmers  End  :  Lodge-Muirhead 
System.  Radio  -  Telegraph  Station  at  Nauen  :  Telefunken 
System.  Station  at  Lyngby  :  Poulsen  System.  The  Lodge- 
Muirhead  System,  the  Marconi  System,  Telefunken  System,  and 
Poulsen  System.  Portable  Stations.  Radio-Telephony.  Ap- 
pendices :  The  Morse  Alphabet.  Electrical  Units  used  in  this 
Book.  International  Control  of  Radio-Telegraphy.  Index. 

The  startling  discovery  twelve  years  ago  of  what  is  popularly  known 
as  Wireless  Telegraphy  has  received  many  no  less  startling  additions 
since  then.  The  official  name  now  given  to  this  branch  of  electrical 
practice  is  Radio-Telegraphy.  The  subject  has  now  reached  a  thor- 
oughly practicable  stage,  and  this  book  presents  it  in  clear,  concise 
form.  The  various  services  for  which  Radio-Telegraphy  is  or  may 
be  used  are  indicated  by  the  author.  Every  stage  of  the  subject  is 
illustrated  by  diagrams  or  photographs  of  apparatus,  so  that,  while 
an  elementary  knowledge  of  electricity  is  presupposed,  the  bearings 
of  the  subject  can  be  grasped  by  every  reader.  No  subject  is  fraught 
with  so  many  possibilities  of  development  for  the  future  relationships 
of  the  peoples  of  the  world. 

India-Rubber  and  its  Manufacture,  with  Chapters 
on  Gutta-Percha  and  Balata.  By  H.  L.  TERRY, 
F.I.C.,  Assoc.Inst.M.M.  With  Illustrations. 

LIST  OF  CONTENTS  :  Preface.  Introduction  :  Historical  and 
General.  Raw  Rubber.  Botanical  Origin.  Tapping  the  Trees. 
Coagulation.  Principal  Raw  Rubbers  of  Commerce.  Pseudo- 
Rubbers.  Congo  Rubber.  General  Considerations.  Chemical 
and  Physical  Properties.  Vulcanization.  India-rubber  Planta- 
tions. India-rubber  Substitutes.  Reclaimed  Rubber.  Washing 
and  Drying  of  Raw  Rubber.  Compounding  of  Rubber.  Rubber 
Solvents  and  then:  Recovery.  Rubber  Solution.  Fine  Cut  Sheet 
and  Articles  made  therefrom.  Elastic  Thread.  Mechanical 
Rubber  Goods.  Sundry  Rubber  Articles.  India-rubber  Proofed 
Textures.  Tyres.  India-rubber  Boots  and  Shoes.  Rubber  for 
Insulated  Wires.  Vulcanite  Contracts  for  India-rubber  Goods. 

(  5  ) 


THE     '  WESTMINSTER  "    SERIES 

The  Testing  of  Rubber  Goods.     Gutta-Percha.     Balata.     Biblio- 
graphy.    Index. 

Tells  all  about  a  material  which  has  grown  immensely  in  com- 
mercial importance  in  recent  years.  It  has  been  expressly  written 
for  the  general  reader  and  for  the  technologist  in  other  branches  of 
industry. 

Glass  Manufacture*  By  WALTER  ROSENHAIN,  Superin- 
tendent of  the  Department  of  Metallurgy  in  the  National 
Physical  Laboratory,  late  Scientific  Adviser  in  the  Glass 
Works  of  Messrs.  Chance  Bros,  and  Co.  With  Illustra- 
tions. 

CONTENTS  :  Preface.  Definitions.  Physical  and  Chemical  Qualities. 
Mechanical,  Thermal,  and  Electrical  Properties.  Transparency 
and  Colour.  Raw  materials  of  manufacture.  Crucibles  and 
Furnaces  for  Fusion.  Process  of  Fusion.  Processes  used  in 
Working  of  Glass.  Bottle.  Blown  and  Pressed.  Rolled  or 
Plate.  Sheet  and  Crown.  Coloured.  Optical  Glass  :  Nature 
and  Properties,  Manufacture.  Miscellaneous  Products.  Ap- 
pendix. Bibliography  of  Glass  Manufacture.  Index. 

This  volume  is  for  users  of  glass,  and  makes  no  claim  to  be  an  ade- 
quate guide  or  help  to  those  engaged  in  glass  manufacture  itself.  For 
this  reason  the  account  of  manufacturing  processes  has  been  kept 
as  non-technical  as  possible.  In  describing  each  process  the  object 
in  view  has  been  to  give  an  insight  into  the  rationale  of  each  step,  so 
far  as  it  is  known  or  understood,  from  the  point  of  view  of  principles 
and  methods  rather  than  as  mere  rule  of  thumb  description  of  manu- 
facturing manipulations.  The  processes  described  are,  with  the 
exception  of  those  described  as  obsolete,  to  the  author's  definite  know 
ledge,  in  commercial  use  at  the  present  time. 

Precious  Stones.  By  W.  GOODCHILD,  M.B.,  B.Ch.  With 
42  Illustrations.  With  a  Chapter  on  Artificial 
Stones.  By  ROBERT  DYKES. 

LIST  OF  CONTENTS  :  Introductory  and  Historical.  Genesis  of 
Precious  Stones.  Physical  Properties.  The  Cutting  and  Polish- 
ing of  Gems.  Imitation  Gems  and  the  Artificial  Production  of 
Precious  Stones.  The  Diamond.  Fluor  Spar  and  the  Forms  of 
Silica.  Corundum,  including  Ruby  and  Sapphire.  Spinel  and 
Chrysoberyl.  The  Carbonates  and  the  Felspars.  The  Pyroxene 
and  Amphibole  Groups.  Beryl,  Cordierite,  Lapis  Lazuli  and  the 
Garnets.  Olivine,  Topaz,  Tourmaline  and  other  Silicates.  Phos- 
phates, Sulphates,  and  Carbon  Compounds. 

An  admirable  guide  to  a  fascinating  subject. 

(  6  ) 


THE     '  WESTMINSTER  "    SERIES 

Patents,  Designs  and  Trade  Marks  :  The  Law 
and  Commercial  Usage*  By  KENNETH  R.  SWAN, 
B.A.  (Oxon.),  of  the  Inner  Temple,  Barrister-at-Law. 

CONTENTS  :  Table  of  Cases  Cited— Part  I.— Letters  Patent.  Intro- 
duction. General.  Historical.  I.,  II.,  III.  Invention,  Novelty, 
Subject  Matter,  and  Utility  the  Essentials  of  Patentable  Invention. 
IV.  Specification.  V.  Construction  of  Specification.  VI.  Who 
May  Apply  for  a  Patent.  VII.  Application  and  Grant.  VIII. 
Opposition.  IX.  Patent  Rights.  Legal  Value.  Commercial 
Value.  X.  Amendment.  XI.  Infringement  of  Patent.  XII. 
Action  for  Infringement.  XIII.  Action  to  Restrain  Threats. 
XIV.  Negotiation  of  Patents  by  Sale  and  Licence.  XV.  Limita- 
tions on  Patent  Right.  XVI.  Revocation.  XVII.  Prolonga- 
tion. XVIII.  Miscellaneous.  XIX.  Foreign  Patents.  XX. 
Foreign  Patent  Laws  :  United  States  of  America.  Germany. 
France.  Table  of  Cost,  etc.,  of  Foreign  Patents.  APPENDIX  A. — 
i.  Table  of  Forms  and  Fees.  2.  Cost  of  Obtaining  a  British 
Patent.  3.  Convention  Countries.  Part  II. — Copyright  in 
Design.  Introduction.  I.  Registrable  Designs.  II.  Registra- 
tion. III.  Marking.  IV.  Infringement.  APPENDIX  B. — i. 
Table  of  Forms  and  Fees.  2.  Classification  of  Goods.  Part 
III. — Trade  Marks.  Introduction.  I.  Meaning  of  Trade  Mark. 
II.  Qualification  for  Registration.  III.  Restrictions  on  Regis- 
tration. IV.  Registration.  V.  Effect  of  Registration.  VI. 
Miscellaneous.  APPENDIX  C. — Table  of  Forms  and  Fees.  INDICES. 
i.  Patents.  2.  Designs.  3.  Trade  Marks. 

This  is  the  first  book  on  the  subject  since  the  New  Patents  Act. 
Its  aim  is  not  only  to  present  the  existing  law  accurately  and  as  fully 
as  possible,  but  also  to  cast  it  in  a  form  readily  comprehensible  to  the 
layman  unfamiliar  with  legal  phraseology.  It  will  be  of  value  to  those 
engaged  in  trades  and  industries  where  a  knowledge  of  the  patenting 
of  inventions  and  the  registration  of  trade  marks  is  important.  Full 
information  is  given  regarding  patents  in  foreign  countries. 

The  Book;  Its  History  and  Development.  By 
CYRIL  DAVENPORT,  V.D.,  F.S.A.  With  7  Plates  and 
126  Figures  in  the  text. 

LIST  OF  CONTENTS  :  Early  Records.  Rolls,  Books  and  Book 
bindings.  Paper.  Printing.  Illustrations.  Miscellanea. 
Leathers.  The  Ornamentation  of  Leather  Bookbindings  without 
Gold.  The  Ornamentation  of  Leather  Bookbindings  with  Gold. 
Bibliography.  Index. 

The  romance  of  the  Book  and  its  development  from  the  rude  inscrip- 
tions on  stone  to  the  magnificent  de  Luxe  tomes  of  to-day  have 
never  been  so  excellently  discoursed  upon  as  in  this  volume.  The 
history  of  the  Book  is  the  history  of  the  preservation  of  human  thought. 
This  work  should  be  in  the  possession  of  every  book  lover. 

(7) 


Van  NostrandV  Westminster"  Series 


LIST    OF    NEW  AND    FORTHCOMING 
VOLUMES. 

The  Gas  Engine.     By  Captain  RYALL  SANKEY, 

M.I.M.E 

Timber.     By  J.  R.  BATERDEN,  A.M.I.C.E. 
Steam  Engines.      By  J.  T.   ROSSITER,   M.I.E.E., 

A.M.I.M.E. 

Electric  Lamps.     By  MAURICE  SOLOMON,  A.C.G.L, 

A.M.I.E.E. 

The  Railway  Locomotive.    By  VAUGHAN  PENDRED, 

M.I.Mech.E. 

Pumps  and  Pumping  Machinery.      By  JAMES  W. 

ROSSITER,  A.M.I.M.E. 

Workshop  Practice.  By  Professor  G.  F.  CHAR- 
NOCK,  A.M.I.C.E.,  M.I.M.E. 

Textiles  and  their  Manufacture.  By  ALDRED  BAR- 
KER, M.Sc. 

The   Precious  Metals.       By  THOMAS   K.    ROSE, 

D.Sc.,  of  the  Royal  Mint. 

Photography.  By  ALFRED  WATKINS,  Past  Presi- 
dent of  the  Photographic  Convention. 

Commercial  Paints  and  Painting.  By  A.  S.  JEN- 
NINGS, Hon.  Consulting  Examiner,  City  and  Guilds  of 
London  Institute. 

Decorative  Glass  Processes.     By  A.  L.  DUTHIE. 
Brewing  and  Distilling.     By  JAMES  GRANT,  F.C.S. 
Wood  Pulp  and  Its  Applications.     By  C.  F.  CROSS, 

E.  J.  BEVAN  and  R.  W.  SINDALL. 

The  Manufacture  of  Paper.     By  R.  W.  SINDALL. 
Wood  Working  Machinery.    By  STAFFORD  RAN- 

SOME. 


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V 


